SpamfilterN_optional MTA options

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Spamfilter MTA options: spamfilterN_optional (-2, -1, 0, 1, 2, 3, 4)

The spamfilterN_optional MTA options control the MTA's reaction when spam/virus filter package N does not respond.

By default (spamfilter*_optional=0), when use of a spam/virus filter package such as Brightmail is configured, a failure to initially connect to the spam/virus filter package, or a failure to get a response from the spam/virus filter package once the filter package has begun processing the envelope addresses or the message itself, will normally result in a temporary error of "4.7.1 filtering/scanning error". (The exact SMTP errors are "452 4.3.0 filtering/scanning error" if the package cannot even be contacted initially, "450 4.7.1 filtering/scanning error" if the package error occurs attempting to process the MAIL FROM: (envelope From:) argument; "452 4.7.1 filtering/scanning error" if the package error occurs attempting to process a RCPT TO: (envelope To:) argument, or "451 4.7.1 filtering/scanning error" if the package error occurs attempting to process the DATA (the message itself). Alternate text in this error message may be configured via the correspondingly numbered error_text_spamfilterN_error MTA options.) Note that for an incoming SMTP message, such a temporary error means that the message is (temporarily) rejected with that error, while for a message that is already on the system and being processed by a reprocess/process/conversion sort of channel, such a temporary error means that the message is reenqueued to the reprocess channel (for the reprocess channel to subsequently reattempt the virus/spam filter package processing).

But when spamfilter*_optional=1 is set, the MTA's message processing will continue even if the spam/virus filter package cannot be accessed or does not complete its processing; that is, messages will be passed through without spam/virus filter package scanning (omitting spam/virus filter package scanning) if the spam/virus filter package scanning is not functioning.

New in MS 6.2 is support for values -2 and 2. Setting a value of 2 is similar to the effect of 1, except that a syslog notice will be generated in case of spam/virus filter package errors. A value of -1 is (currently) equivalent in effect to a value of 0. A value of -2 is similar to a value of 0, except that a syslog notice will be generated in case of spam/virus filter package errors. (See the sndopr_priority MTA option for control of the facility and priority of such syslog notices.)

New in MS 6.3 is support for values 3 and 4. A value of 3 tells the MTA that in case of a virus/spam filter package failure during attempted processing of an incoming message, to accept the message and queue it to the reprocess channel (for subsequent reattempted processing through the virus/spam filter package by the reprocess channel). A value of 4 does the same thing, but also logs the virus/spam filter temporary failure to syslog.

For most site's purposes, either a setting of -2 (meaning to temporarily reject the message, and generate a syslog notice logging the trouble occurrence), or (new in MS 6.3) a setting of 4 (meaning to defer the message to the reprocess channel, and generate a syslog notice logging the trouble occurrence) will be desirable.


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