This chapter summarizes essential information about the Internet Protocols accessed through the Messaging Access SDK.

• Supported SMTP Internet Protocol Commands. SMTP (Simple Mail Transfer Protocol) sends messages.
• Supported IMAP4 Internet Protocol Commands. IMAP4 (Internet Message Access Protocol) retrieves and manages messages remotely.
• Supported POP3 Internet Protocol Commands. POP3 (Post Office Protocol) downloads messages to a client and allows for search and retrieval of messages.
• MIME, Multipurpose Internet Mail Extension. MIME builds code messages with attachments for sending with SMTP, and parses and decodes received messages. SDK MIME methods and functions do not map to a set of Internet Protocol commands in the same way that the other protocols do.

Supported SMTP Internet Protocol Commands

Supported Internet Protocol command	What the command does	SDK function that calls the command
DATA	Informs server that the client is about to send the message. After server OK, client sends RFC 822-compliant message data line by line. On completion, client sends "<CRLF>.<CRLF>" line.	smtp_data
DSN [NOTIFY, RET, ENVID]	Allows SMTP client to generate delivery status notifications (DSNs) when needed, determine whether the notifications return the message contents, and get additional information with a DSN so that the sender can identify both recipient(s) for the DSN and the transaction that contained the original message. (RFC 1891)
EHLO	Client starts SMTP session by sending identification to server; server responds (identifies itself) in a greeting message. EHLO replaces older HELO command for SMTP clients that support SMTP service extensions. Can be issued at the start of the session to see which extensions the server supports.	smtp_ehlo
EXPN	Expands a mailing list alias; the command retrieves the alias member list.	smtp_expand
HELP	Calls the server Help utility. Application-specific; usually lists available commands.	smtp_help
MAIL FROM	Initiates sending the message; supplies the message's reverse path (usually the sender's fully qualified domain name).	smtp_mailFrom
NOOP	Gets positive server response.	smtp_noop
QUIT	Sent by a client to a server when the client is ready to end the session. Server sends response and closes TCP connection. Best to use this command rather than just closing the connection.	smtp_quit
PIPELINING	Allows command pipelining (batching multiple commands into single TCP sends). To find out if server supports pipelining, issue the EHLO command. If it does, the server response includes code 250 and EHLO keyword PIPELINING. Pipelining allows the client to transmit batches of SMTP commands without waiting for a response to each. (RFC 2197)	smtp_setPipelining
RCPT TO	Specifies the address of a message recipient. Called once for each recipient. Follows the MAIL command.	smtp_rcptTo
RSET	Cancels the current mail transfer and all current processes, discards data, and clears session states. Returns to the session state that followed the EHLO command.	smtp_reset
VRFY	Sent by a client to verify a user name with the server. The server responds with a positive or negative code.	smtp_verify

Supported IMAP4 Internet Protocol Commands

Supported Internet Protocol command	What the command does	Session state for command	SDK function that calls the command
APPEND	Appends message to specified mailbox, passes on any message flags.	Authenticated	imap4_append
CAPABILITY	Gets a list of server capabilities.	All states	imap4_capability
CHECK	Requests a checkpoint of the currently selected mailbox; server flushes existing mailbox states to disk.	Selected	imap4_check
CLOSE	Closes a mailbox, deletes flagged messages, moves session to Non-Authenticated state.	Selected	imap4_close
COPY	Copies a message to the specified mailbox.	Selected	imap4_copy
CREATE	Creates a mailbox.	Authenticated	imap4_create
DELETE	Marks a message for deletion.	Authenticated	imap4_delete
EXAMINE	Like SELECT, but read-only.	Authenticated	imap4_examine
EXPUNGE	Removes all messages flagged "\\Deleted" in a mailbox.	Selected	imap4_expunge
FETCH	Returns information from messages. The protocol's FETCH [XSENDER] form is supported.	Selected	imap4_fetch
LIST	Gets list of user names.	Authenticated	imap4_list
LOGIN	Logs in to server with user name and password.	Non-Authenticated	imap4_login
LOGOUT	Ends session; server responds with "BYE."	All states	imap4_logout
LSUB	Lists members of subscription list (must be added with SUBSCRIBE).	Authenticated	imap4_lsub
NAMESPACE	Retrieves the prefixes of namespaces used by a server for personal mailboxes, other user's mailboxes, and shared mailboxes.	All states	imap4_namespace
NOOP	Gets positive server response.	All states	imap4_noop
RENAME	Renames mailbox.	Authenticated	imap4_rename
SEARCH	Finds messages that meet specified criteria.	Selected	imap4_search
SELECT	Selects a mailbox on the server for operations involving messages.	Authenticated	imap4_select
STATUS	Requests one or more types of status for the specified mailbox.	Authenticated	imap4_status
STORE	Updates flags on messages; can return the new flag status.	Selected	imap4_store
SUBSCRIBE	Adds a mailbox to a server's subscribed mailbox list. List is accessed with LSUB.	Authenticated	imap4_subscribe
UID	Used with a command name to specify that it uses unique message identifiers.	Selected	imap4_uidCopy imap4_uidFetch imap4_uidSearch imap4_uidStore
UNSUBSCRIBE	Deletes a mailbox from a server's subscribed mailbox list. List is accessed with LSUB.	Authenticated	imap4_unsubscribe
SETACL	Changes the access control list on the specified mailbox and grants specified permissions.	All states	imap4_setACL
DELETEACL	Removes an <identifier, rights> pair for the specified identifier from the access control list for the specified mailbox.	All states	imap4_deleteACL
GETACL	Retrieves the access control list for the mailbox in an untagged ACL reply.	All states	imap4_getACL
LISTRIGHTS	Retrieves the access control list for mailbox in an untagged ACL reply.	All states	imap4_listRights
MYRIGHTS	Retrieves the user's rights to the specified mailbox.	All states	imap4_myRights

Supported POP3 Internet Protocol Commands

Supported Internet Protocol command	What the command does	Session state for command	SDK function that calls the command
DELE	Asks server to mark specified message for deletion. Deletion actually takes place on entry into Update state.	Transaction	pop3_delete
LIST	Gets the size of one or all messages.	Transaction	pop3_list pop3_listA
NOOP	Gets positive server response.	Transaction	pop3_noop
PASS	Identifies a user password; on success, moves session to the Transaction state.	Authorization	pop3_pass
QUIT	Ends the session. If issued in Authentication state, server closes connections. If issued in Transaction state, server goes into Update and deletes any marked messages, then quits.	Authorization, Update	pop3_quit
RSET	Asks the server to clear all delete tags from messages.	Transaction	pop3_reset
RETR	Requests the entire specified message.	Transaction	pop3_retrieve
STAT	Gets the number of messages in and octet size of mail drop.	Transaction	pop3_stat
TOP	Asks server for first n lines of specified message.	Transaction	pop3_top
UIDL	Gets the unique identifier string for specified or all messages.	Transaction	pop3_uidList pop3_uidListA
USER	Identifies the user or mail drop by name to the server; the server returns a known or unknown response.	Authorization	pop3_user
XAUTHLIST	Returns a list of authenticated users.	Transaction	pop3_xAuthList pop3_xAuthListA
XSENDER	Gets the email address of the sender of the specified message. Client uses this to query whether an individual message has been authenticated. Server returns an empty OK string if no authenticated sender is found.	Transaction	pop3_xSender

Last Updated: June 3, 1998