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| Sun Java System Messaging Server 6 2005Q1 Administration Guide | |
Chapter 16
Vacation Automatic Message ReplyFor automatically generated responses to email (autoreply), specifically vacation messages, the MTA uses Message Disposition Notifications (MDNs) and the Sieve scripting language. MDNs are email messages sent by the MTA to a sender and/or postmaster reporting on a message’s delivery disposition. MDNs are also known as read receipts, acknowledgements, receipt notifications, or delivery receipts. The Sieve is a simple scripting language used to create mail filters.
This section describes the vacation autoreply mechanism. In most cases, modification to the default configuration is unnecessary, but there is a case where you may wish to configure your system such that vacation processing is done on MTA relay machines rather than on back-end message stores.
This chapter consists of the following sections:
Vacation Autoreply OverviewVacation Sieve scripts are generated automatically from the various LDAP vacation attributes (see Vacation Autoreply Attributes). They can also be specified explicitly for additional flexibility. The underlying mechanism for tracking vacations is a set of files, one per intended recipient, that keep track of when replies were sent to the various senders.
By default, the MTA evaluates vacation on the back-end store systems. However, since MTA relays do not do as much work as back-end stores, for performance reasons, you can have the MTA evaluate vacation on the mail relay machines instead of on the back-end store. Use of this feature, however, can result in vacation responses being sent out more often than intended because different relays handle different messages. If you do not want vacation messages to be sent out more often than you intend, you may share the tracking of files between the relays. If this is also unacceptable to you, you can always have vacation evaluated on the back-end store systems.
Configuring AutoreplyDelivery addresses are generated through a set of patterns. The patterns used depend upon the values defined for the mailDeliveryOption attribute. A delivery address is generated for each valid mailDeliveryOption. The patterns are defined by the MTA option DELIVERY_OPTIONS, which are defined in the option.dat file. The default autoreply rule in DELIVERY_OPTIONS in the option.dat file is:
*^!autoreply=$M+$D@bitbucket
The MTA notes the “^” on the autoreply DELIVERY_OPTION MTA option. This causes the MTA to check the vacation dates. If the current date is within the vacation dates, processing continues and the MTA notes the “!” on the autoreply DELIVERY_OPTION. The MTA then creates a vacation Sieve script based on the various autoreply LDAP attributes on the user’s entry. The autoreply rule can have the prefix characters ‘!’, ‘#’, ‘^’, and ‘*’.
You could have the ‘!’ flag on the mailbox delivery option. This would enable the generation of the vacation script unconditionally. It makes sense, however, to have the autoreply machinery enabled by a separate delivery option so that it can be further gated by the ‘^’ flag. Checking the dates at this stage is more efficient than engaging the Sieve logic.
Table 16-1 shows the prefix characters used for the autoreply rule in the first column and their definitions in the second column.
The autoreply rule itself specifies an address destined for the bitbucket channel. The mail is considered delivered by this method once the autoreply is generated, but the MTA machinery requires a delivery address. Anything delivered to the bitbucket channel is discarded.
Configuring Autoreply on the Back-end Store System
The default autoreply rule in DELIVERY_OPTIONS causes the autoreply to take place on the mail server that serves the user. If you want vacation messages to be evaluated on the back-end store system, you do not have to configure anything. This is the default behavior.
Configuring Autoreply on the Relay
If you want to evaluate vacation on the relay rather than on the back-end store system to enhance performance, edit the option.dat file and prepend the character # to the autoreply rule in DELIVERY_OPTIONS. For example:
- Use an editor to open the option.dat file.
- Add or change the DELIVERY_OPTIONS option so the autoreply rule now looks like:
#*^!autoreply=$M+$D@bitbucket
The default DELIVERY_OPTIONS option looks like:
DELIVERY_OPTIONS=*mailbox=$M%$\$2I$_+$2S@ims-ms-daemon, \
&members=*, \
*native=$M@native-daemon, \
/hold=@hold-daemon:$A, \
*unix=$M@native-daemon, \
&file=+$F@native-daemon, \
&@members_offline=* \
,program=$M%$P@pipe-daemon, \
#forward=**, \
*^!autoreply=$M+$D@bitbucketThis allows the processing to take place on relays. If you have the MTA perform autoreplies on the relays, then either each relay can keep track independently of whether a particular correspondent has sent an away message recently, or this information can be shared between the relays. The former case is simpler, especially if having away messages sent out too many times does not matter. If you want strict application of the away message frequency rules, then the information must be shared between relays. To share the information among the relays, the files should be NFS mounted
The location of these files is controlled by the option VACATION_TEMPLATE. This option (in option.dat) should be set to /<path>/%A where <path> is the path to a directory that is shared between the various relay machines. The template needs to be a file:URL and you use $U to substitute the name of the user. The default setting is:
VACATION_TEMPLATE=file:///opt/SUNWmsgsr/data/vacation/$3I/$1U/$2U/$U.vac
See Table 9-6 for metacharacter descriptions.
Vacation Autoreply Theory of OperationThe vacation action, when invoked, works as follows:
- The Sun Java System Messaging Server checks to make sure that the vacation action was performed by a user level rather than a system level Sieve script. An error results if vacation is used in a system level script.
- The “no vacation notice” internal MTA flag is checked. If it is set, processing terminates and no vacation notice is sent.
- The return address for the message is now checked. If it is blank processing terminates and no vacation notice is sent.
- The MTA checks to see if the user's address or any of the additional addresses specified in the :addresses tagged argument appear in a To:, Cc:, Resent-to:, or Resent-cc: header field for the current message. Processing terminates and no vacation notice is sent if none of the addresses is found in any of the header fields.
- The Messaging Server constructs a hash of the :subject argument and the reason string. This string, along with the return address of the current message, is checked against a per-user record of previous vacation responses. Processing terminates and no response is sent if a response has already been sent within the time allowed by the :days argument.
- The Messaging Server constructs a vacation notice from the :subject argument, reason string, and :mime argument. Two basic forms for this response message are possible:
Note that mailautoreplymode is automatically set to reply when vacation messages are configured through Messenger Express.
The “no vacation notice” MTA flag is clear by default. It can be set by a system level Sieve script through the use of the nonstandard novacation action. The novacation Sieve action is only allowed in a system level Sieve script. It will generate an error if it is used in a user level script. You can use this action to implement site-wide restrictions on vacation replies such as blocking replies to addresses containing the substring “MAILER-DAEMON”.
Per-user per-response information is stored in a set of flat text files, one per local user. The location and naming scheme for these files is specified by the setting of the VACATION_TEMPLATE MTA option. This option should be set to a file: URL.
Maintenance of these files is automatic and controlled by the VACATION_CLEANUP integer MTA option setting. Each time one of these files is opened, the value of the current time in seconds modulo this value is computed. If the result is zero the file is scanned and all expired entries are removed. The default value for the option is 200, which means that there is 1-in-200 chance that a cleanup pass will be performed.
The machinery used to read and write these flat text files is designed in such a way that it should be able to operate correctly over NFS. This allows multiple MTAs to share a single set of files on a common file system.
Vacation Autoreply AttributesThe set of user LDAP directory attributes that the vacation action uses are:
Vacation start date and time. The value is in the format YYYYMMDDHHMMSSZ. This value is normalized to GMT. An autoreply should only be generated if the current time is after the time specified by this attribute. No start date is enforced if this attribute is missing. The MTA can be instructed to look at a different attribute for this information by setting the LDAP_START_DATE MTA option to a different attribute name.
This attribute will be read and checked by the code that generated the Sieve script. Vacation processing will be aborted if the current date is before the vacation start date. This attribute cannot be handled by the script itself because at present Sieve lacks date/time testing and comparison facilities.
Vacation end date and time. The value is in the format YYYYMMDDHHMMSSZ. This value is normalized to GMT. An autoreply should only be generated if the current time is before the time specified by this attribute. No end date is enforced if this attribute is missing. The MTA can be instructed to look at a different attribute for this information by setting the LDAP_END_DATE MTA option to a different attribute name.
This attribute will be read and checked by the code that generated the Sieve script. Vacation processing will be aborted if the current date is after the vacation end date. This attribute cannot be handled in the script itself because at present Sieve lacks date/time testing and comparison facilities.
Specifies autoreply mode for the user mail account. Valid values of this attribute are:
These modes will appear in the Sieve script as nonstandard :echo and :reply arguments to the vacation action. echo will produce a “processed” message disposition notification (MDN) that contains the original message as returned content. reply will produce a pure reply containing only the reply text. An illegal value will not manifest as any argument to the vacation action and this will produce an MDN containing only the headers of the original message. Note also that selecting an autoreply mode of echo causes an automatic reply to be sent to every message regardless of how recently a previous reply was sent.
The MTA can be instructed to use a different attribute for this information by setting the LDAP_AUTOREPLY_MODE MTA option to a different attribute name.
Specifies the contents of the subject field to use in the autoreply response. This must be a UTF-8 string. This value gets passed as the :subject argument to the vacation action. The MTA can be instructed to use a different attribute for this information by setting the LDAP_AUTOREPLY_SUBJECT MTA option to a different attribute name.
Note that because Sieve currently lacks the ability to perform certain substitutions at present, use of $SUBJECT to insert the original message into the header cannot be implemented.
Auto-reply text sent to senders from the recipients domain. If not specified, then internal users get the mail autoreply text message. The MTA can be instructed to use a different attribute for this information by setting the LDAP_AUTOREPLY_TEXT_INT MTA option to a different attribute name.
The MTA will pass either the mailAutoReplyText or mailAutoReplyTextInternal attribute value as the reason string to the vacation action.
Duration, in hours, for successive autoreply responses to any given mail sender. Used only when mailAutoReplyMode=reply. If value is 0 then a response is sent back every time a message is received. This value will be converted to the nonstandard :hours argument to the vacation action. (Normally the Sieve vacation action only supports the :days argument for this purpose and does not allow a value of 0.)
If this attribute doesn't appear on a user entry, a default time-out will be obtained from the AUTOREPLY_TIMEOUT_DEFAULT MTA option. The MTA can be instructed to use a different attribute for this information by setting the LDAP_AUTOREPLY_TIMEOUT MTA option.