Messaging Server Administrator's Guide: Configuring SMTP Services

Safe group ID for running programs. In this field, type the safe Unix group ID for running programs set up for the root account. The safe Unix user ID should be a member of the safe group ID.

Click Save.

See also SMTP System Tab in the Interface Reference section.

Deferring Delivery

By default, the Messaging Server attempts to deliver messages immediately; the server queues mail only if there is a problem. You can specify that Messaging Server queue all outgoing mail and attempt delivery only when it processes the message queue. The server processes the message queue on intervals you indicate. For more information, see Managing the Message Queue.

This option is most useful for businesses that do not maintain a continuous connection to the Internet, but use dial-up connections instead. For example, the Messaging Server can dial out to a remote host and then process the mail queue for the remote host.

To specify deferred delivery, go to the SMTP Accept window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

Check the "Defer delivery to remote hosts" box.

Click Save.

If you are specifying deferred delivery, you might also want to turn on the SMTP command, ETRN, to enable requests for deferred queue processing. With deferred queue processing, when a client (in this case, another MTA) connects to the server to send a message, it can also initiate processing of the deferred queue for the client domain. For more information, see Enabling Requests for Deferred Queue Processing (ETRN).

See also SMTP Accept Tab in the Interface Reference section.

Verifying Recipient Addresses

You can specify that the Messaging Server verify recipient addresses for messages it accepts from clients.

By enabling this option, the server can detect bad recipient names in the envelope address and return an error to the client before the client sends the body of the message. The client can fix the name before sending the message text.

Specifying this option has slight performance impact because the server must perform an LDAP lookup for each recipient while connected to the client. The benefit, however, is that bad recipients can be rejected immediately, allowing the sender to fix before sending (instead of getting a bounce message later).

To specify verification of recipient addresses, go to the SMTP Accept window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

Check the "Verify each recipient's address" box.

Click Save.

See also SMTP Accept Tab in the Interface Reference section.

Performing Host Name Resolution

You can specify that the Messaging Server perform host name resolution for messages it accepts from clients.

Using the client's IP address, the Messaging Server will use DNS to find the associated host name. The Messaging Server will subsequently refer to client machines by host name instead of IP address. For example, host names will be used in the process table, the log file, and "Received" lines in message headers.

Note: If you handle a large volume of messages, be aware that selecting this option impacts performance adversely.

To specify that the server should perform host name resolution, go to the SMTP Accept window.

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

Check the "Lookup client machine names" box.

Click Save.

See also SMTP Accept Tab in the Interface Reference section.

Specifying the Number of MTA Hops

Each MTA stamps all incoming messages as Received. By counting the number of Received lines in the message header, the MTA can determine how many MTAs have already handled this message. The act of routing a message from one MTA to another is called a hop or an MTA hop. Each time an MTA handles a message, the message has taken another hop.

To deliver a message might require many hops. You might want to limit the number of hops for various reasons; for example, to prevent infinite mail loops. If the number of hops exceeds the maximum you specify, the message is bounced and the server returns an error message.

To specify the maximum number of MTA hops, go to the SMTP Accept window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

In the "Maximum number of MTA hops" field, specify a number.

The recommended range for this parameter is 30 or more. The default number is 30.

Click Save.

See also SMTP Accept Tab in the Interface Reference section.

Reserving Free Disk Space

You can specify a minimum amount of disk space that will remain unused for the message queue. If the minimum threshold is reached, the server will temporarily reject all messages until disk space is freed. The server returns an error (452) notifying the client of a temporary disk space shortage and asking the client to resend the message at a later time.

The server can also reject messages based on message size. For more information about specifying a maximum message size, see Limiting Message Size (SIZE).

To reserve free disk space, go to the SMTP Accept window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

In the "Minimum free disk space" field, specify a number.

From the pull-down menu beside the field, specify Kbytes or Mbytes.

Click Save.

See also SMTP Accept Tab in the Interface Reference section.

Expanding SMTP Dialogs

Netscape Messaging Server 4.0 supports several SMTP commands for enabling extra functionality in the dialog between an SMTP client (either a UA or another server) and the Messaging Server.

To enable these commands, go to the SMTP Accept window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Accept. The SMTP Accept window appears.

From this window, you can enable SMTP commands for the following:

Verifying User Names (VRFY)

Verifying a Mailing List (EXPN)

Enabling Requests for Deferred Queue Processing (ETRN)

Limiting Message Size (SIZE)

See also SMTP Accept Tab in the Interface Reference section.

Verifying User Names (VRFY)

The VRFY command enables clients to send a request to your server to verify that mail for a specific user name resides on the server.

The server sends a response indicating whether the user is local or not, whether mail will be forwarded, and so on. A response of 250 indicates that the user name is local; a response of 251 indicates that the user name is not local, but the server can forward the message. The server response includes the mailbox name. The VRFY command is defined in RFC 821.

To enable verification of user names:

Go to the SMTP Accept window.

Check the "Allow SMTP command VRFY" box to enable the SMTP command for verifying a user name.

Click Save.

Caution: Because the server response might include user IDs, do not enable this option unless you are willing to reveal user IDs to clients accessing your server.

Verifying a Mailing List (EXPN)

If both the client and the server support the SMTP EXPN command, clients can make requests to your server to verify that a particular mailing list resides on the server. The EXPN command is defined in RFC 821.

To enable verification of mailing lists on your server:

Go to the SMTP Accept window.

Check the "Allow SMTP command EXPN" box to enable the SMTP command for verifying a user name.

Click Save.

Caution: Do not enable this option unless you are willing to acknowledge mailing lists to clients accessing your server.

Enabling Requests for Deferred Queue Processing (ETRN)

If both client (in this case another MTA) and server support the ETRN command, when the client connects to the server to send a message, it can also initiate processing of the deferred queue for the client domain. For security reasons, the server starts a new connection to the client machine before sending messages to the client. The ETRN command is defined in RFC 1985.

This feature is useful for sites that only have a dial-up connection to the Internet. By enabling this command, you can improve server performance by limiting the number of dial-up connections to your server.

To enable requests for deferred queue processing:

Go to the SMTP Accept window.

Check the "Allow SMTP command ETRN" box to enable the SMTP command for enabling requests for deferred queue processing.

Click Save.

Limiting Message Size (SIZE)

If both client and server support the SIZE command, clients can declare the size of a particular message to the server, and the server can accept or reject the message based on its size. Any attempts to send a message larger than the specified size will automatically fail and the server will return an error message (552) indicating that the message size exceeds the maximum allowed. The SIZE command is defined in RFC 1870.

The server can also reject a message temporarily if it is running low on disk space. For more information, see Reserving Free Disk Space.

To limit the size of messages your server accepts:

Go to the SMTP Accept window.

Check the "Allow SMTP command SIZE" box to enable the SMTP SIZE command.

Indicate the maximum size message the server will accept by typing a number in the field beside the checkbox and choosing MBytes or KBytes from the pull-down menu.

Click Save.

Specifying Automatic Reply Information

You can specify automatic reply messages for several situations. For example, you can specify a default vacation reply message for users who do not write a personalized message or you can specify a default reply for messages sent to a particular address.

To specify automatic reply information, go to the SMTP Autoreply window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Autoreply. The SMTP Autoreply window appears.

From the pull-down menus for each field, choose the language of your choice.

Type the default messages for each of the reply fields:

Default vacation-mode reply message. Type an automatic reply for users who do not write a personalized vacation message.

Anyone who sends messages to a user's account while the vacation setting is activated will receive one notice about the user's absence. Any subsequent messages that person sends are ignored.

In most cases, you should not replace a user's current delivery with the vacation setting when they set up the AutoReply handler for that user's account. If you do this, the user will return from vacation only to find that all of his or her email has been thrown away. Rather, you should use the vacation setting in addition to the normal delivery method, so mail is held for the user to retrieve upon his or her return. (Users are prevented from making this mistake because the Messaging Server doesn't accept account management forms with a delivery of "Vacation" only.)

Default echo-mode reply message. Type an automatic reply for the server's echo feature. A common use of the echo feature is to return mail addressed to people who have moved on and left no forwarding address.

The echo feature generates a message to anyone who sends a message to the account. In addition, it returns the mail (as a MIME attachment) that was sent to the account, so that the sender gets back the original message as well as the message that you entered.

The echo feature, like the vacation feature, is intended to inform people about the status of the account they have contacted.

Default reply-mode reply message. Type an automatic reply for the server's default reply mode.

The default reply feature is useful for special accounts that are created to disseminate information of one kind or another. You can create a place where people can get files, analogous to a File Transfer Protocol (FTP) site on the Internet.

Click Save

See also SMTP Autoreply Tab in the Interface Reference section.

Specifying Error Handling

There are various situations in which an MTA cannot deliver or route a message. For example, the most common are when an address refers to an unknown local account, when the maximum number of MTA hops is exceeded, or when disk quota is exceeded.

To specify error handling instructions, go to the SMTP Error window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Error. The SMTP Error window appears.

For each error situation, choose one of the following error handling methods:

Return message to sender

Notify the postmaster via email

Log the error in the log file

Click Save.

See also SMTP Error Tab in the Interface Reference section.

Specifying Routing and Addressing Information

For detailed conceptual information about routing and addressing, including information about envelope rewrite methods, alternate search methods, and the SMTP routing table, see Chapter 9, Message Routing.

To specify routing and addressing information, go to the Address window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click Address. The SMTP Address window appears.

From this window, you can perform the following tasks:

Specifying Envelope Rewrite Methods

Specifying From Address Rewrite Style

Specifying Alternate Search Methods

Editing SMTP Routing Table Entries

Note: You should shut down your server before specifying configuration changes on this form.

See also SMTP Address Tab in the Interface Reference section.

Specifying Envelope Rewrite Methods

You can specify whether and how the server rewrites the envelope recipient address before routing a message to a remote MTA. To specify envelope rewrite methods:

Go the SMTP Address window.

Check one or more of the following boxes:

Use the mailRoutingAddress attribute. This method is most useful for LDAP entries that represent mail accounts on non-Netscape mail servers or gateway systems.

Note that you must also modify the user's LDAP entry (by using ldapmodify) to include the mailRoutingAddress attribute.

Combine the uid with the mailHost attribute. With this method, the server combines the uid attribute and the mailHost attribute found in the LDAP directory for rewriting the envelope address.

For example, mail arrives on one server for Joe_Smith@airius.com. The server determines that this mail belongs to jsmith whose mail account is on judge.airius.com. The server rewrites the envelope address to jsmith@judge.airius.com then relays the message to judge.airius.com.

This method is most likely to work properly if the "uid" search method is employed on the next server.

Some sites prefer that only explicit addresses (that is, those addressed specified by the mail and mailAlternateAddress attributes) are valid email addresses for users. You should not use this method if the local policy does not consider uid a valid email address.

Combine the local part of the address with the mailHost attribute. With this method, the server combines the local part of the original address with the mailHost attribute value to create the new address.

For example, Customer_Service@airius.com becomes Customer_Service@judge.airius.com. This method is useful to support entities, such as mail groups, that do not have a uid.

This method is not used if the "custom domain" search method is used to resolve the address. You should not use this rewrite method if changing the domain part to a specific host creates ambiguity about the message recipient.

Click Save.

The default method is to use the original address unmodified.

Specifying From Address Rewrite Style

Rewriting the "From:" address increases the odds that replies to outgoing messages are processed correctly. For example, often the address that a mail client inserts in the "From:" line isn't the best choice. To specify how the server should rewrite the "From" address:

Go to the SMTP Address window.

From the "From address rewrite style" pull-down menu, choose one of the following rewrite styles:

"john doe"<jdoe@company.com>. Choose this option to rewrite the address in the style indicated.

jdoe@company.com (John Doe). Choose this option to rewrite the address in the style indicated.

jdoe@company.com. Choose this option if you want the server to try to complete an incomplete address.

never rewrite addresses. Choose this option if you do not want the server to rewrite any part of the from address.

You might want to choose this option, for example, if you have a plug-in program that performs address rewrites. Or, for another example, in a multilingual environment where you trust the sender to use the appropriate alphabet and do not want to modify the address.

Click Save.

Specifying Alternate Search Methods

You can expand the list of possible recipient matches by specifying one or more of the following search methods. If all search methods are specified, the server tries each method in the order listed until a match is found. The default setting is search on user ID only.

To specify alternate search methods:

Go to the SMTP Address window.

Check one ore more of the following boxes:

Search for custom domain. Check this box if you want the server to use the "custom domain" search method.

Assume Joe has two addresses with his ISP: joe@isp.com and a custom domain address, joecorp.com. To enable Joe to receive mail addressed to anything@joecorp.com, you must add a MailAlternateAddress value for Joe as follows: @joecorp.com. You must also add the MX records in DNS as necessary to indicate the desired messaging server for the custom domain. For more information about DNS and MX records, see The Domain Name System (DNS) in Chapter 9.

Search using truncated domain. Check this box if you want the server to use the "truncated domain" search method.

In a network environment, you might want the option of ignoring the host name when searching for an address. For example, assume the following: The value for MessageHostName is foo.airius.com; Joe's email address is joe@airius.com. With this feature enabled, the server can ignore the host name foo when searching in the directory for the correct address. Consequently, Joe can receive messages addressed to both joe@foo.airius.com and joe@airius.com.

You should use this feature only if user accounts are not specific to a particular host. For example, if user@host1.domain.com, user@host2.domain.com, and user@domain.com are considered different accounts, do not enable this feature.

Search by user ID. Check this box if you want the server to use the "user ID" search method.

The server can search on the user ID only if 1) the domain in the address matches one of the host values specified for the MessageHostName parameter or 2) the domain is configured as a local mail domain.

With this feature enabled, each user's uid attribute in LDAP is a valid email address for that user in an address such as uid@LocalMailDomain or uid@MessageHostName.

Do not use this feature if you do not want the user's uid to be treated as a valid email address.

Click Save.

Note: Specifying alternate search methods has a slight impact on performance.

Editing SMTP Routing Table Entries

If the Messaging Server assumes another mail server is responsible for this recipient, the Messaging Server checks its mail routing table to see if mail for the recipient's domain should be routed to a specific mail server host.

Entries in the mail routing table are processed in order. You should keep this in mind when creating entries. For example, if you have an entry that sends all non-local mail to a firewall mail server, you want this entry to be the last entry in the routing table.

To edit SMTP routing table entries:

Go to the SMTP Address window.

Click the Add button by the SMTP routing table field.

Type a routing table entry.

Click OK to return to the SMTP Address window.

Click Save.

Example Routes

The following example routes all internal mail through a hub server:

*.airius.com:hub.airius.com

The next example forces the use of IP addresses for frequently called servers (bypassing DNS):

hub.airius.com:[123.345.456.7]

The next example shows the use of a firewall server for all outside mail:

*airius.com:*
*:firewall.airius.com

Controlling Access to SMTP Services

Netscape Messaging Server provides several features that enable you to control access to your SMTP services. These features include:

Specifying authenticated SMTP

Specifying access control filters

Filtering unsolicited bulk email (UBE)

Netscape Messaging Server also supports the Secure Sockets Layer (SSL) protocol for transferring private data over TCP/IP networks. For details about determining the access control and security requirements for your server, see Chapter 6, Security and Access Control.

Specifying Authenticated SMTP

Authenticated SMTP provides for greater security in sending messages using the SMTP protocol. To use authenticated SMTP, you do not need to deploy a certificate-based infrastructure. However, authenticated SMTP does not provide the same level of security features as a certificate-based infrastructure.

With authenticated SMTP, the client (either a user agent or another server that supports authenticated SMTP) can indicate an authentication mechanism to the server, perform an authentication protocol exchange, and optionally negotiate a security layer for subsequent protocol interactions. For example, when supported by the user's mail client, authenticated SMTP can require users to enter a password before they are allowed to send messages.

For more information about authenticated SMTP, and when and how to use it in your security and access scheme, see Chapter 6, Security and Access Control.

To specify authenticated SMTP, go to the SMTP System window:

In the Messaging Server Console, select the Configuration tab.

Open the Services folder.

Click SMTP. The SMTP configuration tabs appear in the right pane.

Click System. The SMTP System window appears.

Check the "Allow password login" box.

Specify a minimum cipher length for password encryption.

A cipher is the algorithm used to encrypt and decrypt data in the encryption process. A cipher operates on data by applying a key--a long number--to the data. Generally, a longer key represents a more secure encryption process.

Caution: If you specify 0, the server does not encrypt passwords. Do not specify 0 if you are concerned about sending passwords in clear text. Choose 40 or 128 to ensure that passwords are sent over secure channels.

Click Save.

See also SMTP System Tab in the Interface Reference section.

Specifying Access Control Filters

You can define access control filters to exclude spammers and DNS spongers from your system and improve the general security of your network.

For detailed information about TCP client access control features including complete filter syntax, see the chapter entitled Chapter 6, Security and Access Control. For details about how to define access control filters for your SMTP services, see Creating Access Filters with Netscape Console in Chapter 6.

Filtering Unsolicited Bulk Email

Unsolicited Bulk Email (UBE) is email sent to large number of recipients without their knowledge or consent, often advertising commercial products or services. It is the electronic equivalent of paper "junk mail."

Netscape Messaging Server provides an SMTP UBE plugin you can use to design and implement filters that block unsolicited bulk email from reaching your servers.

For details about the UBE plugin and how to use it to filter unwanted mail, see Chapter 8, Filtering Unsolicited Bulk Email.

Working With SMTP Plugins

Netscape Messaging Server 4.0 provides an application programming interface (API) that allows third parties to create server plugins that can add site-specific functionality to the Messaging Server.

For details on working with SMTP plugins, see Chapter 7, Working With SMTP Plug-Ins.

Managing the Message Queue

By default, the Messaging Server attempts to deliver messages immediately; the server queues mail only if there is a problem, or if you have explicitly specified deferred delivery to other servers. (For information about specifying deferred delivery, see Deferring Delivery.)

This section discusses two types of queues: logical queue and physical queue.

Logical Queue. Logical queue refers to the active queue (the messages currently being processed) and one or more deferred queues (messages that are queued for future delivery).

Deferred messages are grouped by domain. If the server cannot deliver mail to a domain, it automatically creates a logical queue based on the domain part of the message address and the physical queue containing the message.

You can manage logical queues as described in the following sections:

Specifying Actions on Logical Queues

Enabling Requests for Deferred Queue Processing (ETRN)

Physical Queue. A physical queue refers to where and how messages are stored on disk. You can specify alternate path names for physical queue directories, as described in Specifying Alternate Paths for Queue Storage.

About the Queue Directories

Logical queues are stored across three physical queue directories: control, deferred, messages.

The control Directory

The control directory contains the information necessary to process messages in the active queue--the queue that the Messaging Server is currently processing.

When the server accepts a message, it logs an entry in the control directory. When the server is finished processing the message (the message has been delivered to the user's inbox, the message has been deferred, or the message has been relayed), the server logs another entry in the control directory.

The control directory entries contain pointers to files in the messages directory.

The deferred Directory

The deferred directory contains the control information for messages that have been deferred. This directory contains one file to record the information about deferred messages.

The deferred directory entries contain pointers to the files in the messages directory.

The messages Directory

The messages directory contains the text (header and body) of all messages in the active and deferred queues. This directory contains one file per message.

Specifying Actions on Logical Queues

You can specify whether to return messages to the sender, move messages to the active queue, or delete messages from the queue.

To specify actions on a logical message queue, go to the Queued Messages window:

In the Messaging Server Console, select the Configuration tab.

Open the Services Folder.

Click SMTP.

Click Message Queue. The Message Queue configuration tabs appear in the right pane.

Click Queued Messages. The Queued Messages window appears.

Select a queue from the list.

Click the Select Action button.

Select an action from the pop-up window and click OK.

Click Save.

See also Queued Messages Tab in the Interface Reference section.

You can enable requests for processing of deferred queues to limit the number of dial-up connections to your server. With deferred queue processing, when a client (in this case another MTA) connects to the server to send a message, it can also initiate processing of the deferred queue for the client domain. For more information, see Enabling Requests for Deferred Queue Processing (ETRN).

You can also perform actions on the queue from the command line interface. For more information about the command line utilities for managing the queue, see mailq and processq in Appendix A.

Specifying Alternate Paths for Queue Storage

You can specify alternate MTA queue paths for the physical queue directories: control, messages, and deferred..

By specifying alternate MTA queue paths, you can distribute the load associated with delivering a message because the server can perform concurrent I/O operations. You can also reduce the overhead associated with large numbers of files accumulating in a single message queue.

To specify an alternate path for queue storage, go to the Message Queue Configuration window:

In the Messaging Server Console, select the Configuration tab.

Open the Services Folder.

Click SMTP.

Click Message Queue. The Message Queue configuration tabs appear in the right pane.

Click Configuration. The Message Queue Configuration window appears.

Click the Add button beside the Queue path field.

Type a queue path and click OK.

Click Save.

See also Message Queue Configuration Tab in the Interface Reference section.

Interface Reference: SMTP Configuration

This section describes the Messaging Server interface elements that allow you to configure and execute the server's SMTP services. You access these elements through Netscape Console; see Managing Servers With Netscape Console for information on using Netscape Console to manage the Messaging Server and other Netscape servers.

SMTP System Tab

You use the form accessed through the SMTP System tab to specify information about domains, authenticated SMTP, and delivery options. For more information, see also:

Viewing and Configuring Domain Information

Specifying Authenticated SMTP

Specifying Delivery Options

Domains

Address completion domain. In this field, type the name of the DNS domain that will be used to complete a recipient address if the address does not contain a domain name.

Local domain. This field displays the mail domains handled by this MTA. You can add a domain or edit the contents of this field by clicking one of the following three buttons. Mail sent to an unknown recipient at any of these domains is either forwarded to another host if possible or bounced.

Add. Click this button to bring up a window (see Add Domain Window) that allows you to add a new domain to the Local Domain field.

Edit. Click this button to bring up a window that allows you to edit the domain that is currently highlighted in the Local Domain field.

Delete. Click this button to delete the domain that is currently highlighted in the Local Domain field.

Authenticated SMTP

Allow password login. Check this box to allow authenticated SMTP.

Minimum cipher length for password encryption. Choose the minimum cipher length for password encryption from the pulldown menu: 0, 40, or 128.

Unix Delivery

Local mail delivery program. In this field, type the path of the Unix mail delivery program to which the Messaging Server should deliver mail for accounts with the Unix-delivery option enabled.

For more information about Unix delivery, see Delivering Mail to Unix Mail Folders earlier in this chapter.

Program Delivery

Safe user ID for running programs. In this field, type the safe Unix user ID for running programs set up for the root account.

Safe group ID for running programs. In this field, type the safe Unix group ID for running programs set up for the root account. The safe Unix user ID should be a member of the safe group ID.

For more information about program delivery, see Delivering Mail to a Program earlier in this chapter.

Action Buttons

Save. Click this button to save settings you have made in the SMTP System window.

Reset. Click this button to reset the window to the current server settings.

Help. Click this button to get online help (this document) describing the SMTP System window.

Add Domain Window

You use the Add Domain window to add a domain to the list of domains handled by this MTA. For more information, see also:

Viewing and Configuring Domain Information

Specifying the Domains Local to Your Server

The Domain Name System (DNS)

Domain handled by this server exclusively. Type the domain name you want to add.

OK. Click this button to add the domain to the list of local domains on the SMTP System window.

Note that changes are not saved until you click Save on the SMTP System window.

Cancel. Click this button to cancel edits you've made to the Add Domain window.

Help. Click this button to get online help (this document) describing the Add Domain window.

SMTP Accept Tab

You use the form accessed through the SMTP Accept tab to specify information about message delivery, address verification, host name resolution, the maximum number of MTA hops allowed, minimum free disk space, and whether the server allows various SMTP commands. For more information, see also:

Deferring Delivery

Verifying Recipient Addresses

Performing Host Name Resolution

Specifying the Number of MTA Hops

Reserving Free Disk Space

Expanding SMTP Dialogs

Defer delivery to remote hosts. Check this box to defer delivery to remote MTAs. If you check this option, the Messaging Server queues all outgoing mail and attempts delivery only when it processes the message queue.

Verify each recipient's address. Check this box if you want the Messaging Server to verify each address listed as a recipient. The Messaging Server returns an error for local addresses that are not found in the Directory Server.

Lookup client machine names. Check this box if you want the Messaging Server to perform host name resolution for all connecting client machines.

Maximum number of MTA hops. In this field, type the maximum number of times a message can be routed from one MTA to another. The recommended range for this parameter is 30 or more. The default number is 30.

Minimum free disk space. In this field, type the minimum amount of disk space that should remain free. You can specify MBytes or KBytes from the pull-down menu. If disk space gets too low according to the value you specify, the server will reject messages temporarily.

Allow SMTP command `VRFY'. Check this box to enable the SMTP command for verifying a user name.

Caution: Because the server response might include user IDs, do not enable this option unless you are willing to reveal user IDs to clients accessing your server.

Allow SMTP command `EXPN'. Check this box to enable the SMTP command for verifying a mailing list. If both client and server support the EXPN command, clients can make requests to your server to verify that a particular mailing list resides on the server.

Caution: Do not enable this option unless you are willing to acknowledge mailing lists to clients accessing your server.

Allow SMTP command `ETRN'. Check this box to enable the SMTP command for enabling requests for deferred queue processing.

Allow SMTP command `SIZE'. Check this box if you want to enable client/server dialog about message size. Indicate the maximum size the message the server will accept by typing a number in the field beside the checkbox and choosing MBytes or KBytes from the pull-down menu.

Action Buttons

Save. Click this button to save settings you have made in the SMTP Accept window.

Reset. Click this button to reset the window to the current server settings.

Help. Click this button to get online help (this document) describing the SMTP Accept window.

SMTP Autoreply Tab

You use the form accessed through the SMTP Autoreply tab to specify automatic reply messages for various situations. For more information, see also Specifying Automatic Reply Information.

Default vacation-mode reply message. In this field, type the vacation message that will be used if users do not write a personalized message. The MTA automatically sends this reply message for a user account whose vacation setting is activated.

Default echo-mode reply message. In this field, type a generic message for users sending messages to this address. A common use of the echo feature is to return mail addressed to people who have moved on and left no forwarding address.