Standard Handlers
Overview
The most useful protocol front-ends and delivery back-ends are joined
by a set of standard handlers. These handlers integrate the operation
of mail rules, pattern matching, several miscellaneous options
and back-end validation and delivery functions.
Features
The following features are common to all front-ends that use the
standard handlers:
- Validates senders and recipients according to mail rules processing.
- Requires all addresses except the null sender to contain a fully
qualified domain name.
- If $RELAYCLIENT is set, all recipient addresses not
rejected by mail rules are allowed, and its contents are appended to
each recipient address. Back-end validation is omitted.
- Rejects messages that exceed $DATABYTES bytes in length.
- Counts the number of "Received:" and
"Delivered-To:" headers, and rejects the message if more than
$MAXHOPS of either are seen (defaults to 100).
- Optionally adds a fixup "Received:" header for hosts that
have different incoming and outgoing hostnames or IPs. Set
$FIXUP_RECEIVED_HOST and $FIXUP_RECEIVED_IP if you
want this header added.
- Optional user-specified headers may be added by setting
$HEADER_ADD.
- If $CVM_LOOKUP is set, recipients are sent to the named CVM
to see if they are valid. If CVM_LOOKUP_SECRET or
$LOOKUP_SECRET are set and not empty, the value is sent as a
single credential to the CVM.
- If $MAXRCPTS is set, the number of recipients allowed per
message is limited to that number.
- Support for pattern matching in the
message data.
- Support for adding additional plugins at run time. Set
$PLUGINS to a colon separated list of plugin names, and
optionally set $MODULE_PATH to the directory in which those
plugins are contained.
- If $PLUGINS includes require-auth, all mail is
rejected unless either $RELAYCLIENT is set or the sender
authenticates.