Message acceptance

Just after when Sympa's sympa_msg.pl daemon fetches an incoming message from the incoming spool ($SPOOLDIR/msg directory), it executes some sorts of inspection on the message, and will ignore the message that does not meet certain requirements.

Additionally, list owners may choose customized policies based on authorization scenario so that they can control message acceptance.

Checkpoints built in Sympa

Some of requirements by Sympa are mandatory and the others are optional. The messages ignored according to any of requirements will be kept in the bad directory in incoming spool and will no longer be processed.

Existence of mandatory header fields

• If the message did not have Messsage-ID: header field, it will be ignored.

• If the message did not have available sender address, it will be ignored. The "sender address" is an originator address of the message suggested by message header fields. By default, it is taken from From: header field (See also "sender_headers" parameter).

Loop prevention

• Some sorts of automated messages may be ignored. This feature is enabled by default (See reject_mail_from_automates_feature).

  • If sender address (see above) includes any of well-known mailbox names, it may be ignored (See loop_prevention_regex).

  • If message header contains a field signifying automated message, message will be ignored. In particular, Auto-Submitted: (RFC 3834), Conntent-Identifier: (nonstandard) and X400-Conntent-Identifier: (RFC 2156) are supported.

  • If incoming message has X-Loop: header field including the same address as target list, the message will be ignored.

  On the other hand, Sympa adds Auto-Submitted: field to the messages generated by mailing list system itself, and adds X-Loop: adds X-Loop: header field to the messages delivered by Sympa itself.

• If already known message ID was found, the message will be ignored. sympa_msg.pl keeps message IDs of recently delivererd messages and detects duplication. This feature cannot be disabled.

See also "Loop prevention".

The other criteria

• Sympa can ignore message that looks containing "mail commands" (See "misaddressed_commands" parameter).

• Sympa can ignore message that excceeds specified message size (See "max_size" parameter).

• Optional Antivirus plug-in may ignore the message containing potentially insecure content (See "Antivirus plug-in").

Check by authorization scenario

The list owner can choose send authorization scenario to control who can send to the list (See also "Authorization scenarios" and "send" parameter).

This scenario may return one of following results:

• do_it

  Accepting message. Afterwards, the message will be altered as neccesity (see "Message alteration") and delivered to list members (see "Message delivery").

• editor

  Forwarding to moderators. The message will be forwarded to list moderator(s) so that they may re-post it to the list by theirselves.

• editorkey

  Holding message for moderation. The message will be held in the moderation spool and wait for moderation by list moderator. Only the messages authorized by moderators will be delivered through the list.

• request_auth

  Holding message for confirmation. The message will be held in the authorization spool and wait for confirmation by the sender. Only the messages authorized by sender will step forward to further processing such as delivery.

• reject

  Denying message. The message will no longer be delivered to list members. Unless "quiet" modifier is specified, deliovery status notification will be sent back to the sender.