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Fix message to avoid classification as spam

Lukas Jelinek requested to merge message-id into master

It contains two changes that should help to avoid classification of notification messages as spam.

  • It replaces a domain extracted from the user_notify.smtp.from variable (it almost never contains a domain) by the turris_email_domain (i.e., notify.turris.cz). This should prevent the INVALID_MSGID spam flag caused by Message-ID containing no domain.
  • It adds the Content-Transfer-Encoding header set to 8bit. This should prevent the CTE_8BIT_MISMATCH spam flag caused by the combination of the (default) 7bit transfer encoding with 8bit message bodies.

Reported by @mbehun (originally from IRC):

19:51:14   gps │ I do not think anyone from Turris team monitors this channel anymore, but a quick post since mail notifications sent by Turris are being tagged as spam by SpamAssassin:
19:51:27   gps │  3.6 RCVD_IN_SBL_CSS        RBL: Received via a relay in Spamhaus SBL-CSS
19:51:29   gps │                             [172.59.212.76 listed in zen.spamhaus.org]
19:51:41   gps │  1.2 INVALID_MSGID          Message-Id is not valid, according to RFC 2822
19:51:43   gps │  1.0 CTE_8BIT_MISMATCH      Header says 7bits but body disagrees
19:52:52   gps │ All of that should be fixed/addressed by Turris team.
19:56:04   gps │ I guess if a home network IP (IP above is not my home) is on a blocklist of consumer ISP IPs, that will be flagged.
Edited by Lukas Jelinek

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