35 lines
1.6 KiB
Markdown
35 lines
1.6 KiB
Markdown
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title = "block mails for unknown users"
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date = "2014-01-16T09:01:01+00:00"
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author = "Gibheer"
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draft = false
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Postfix' policy system is a bit confusing. There are so many knobs to avoid
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receiving mails which do not belong to any account on the system and most of
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them check multiple things at once, which makes building restrictions a bit of
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a gamble.
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After I finally enabled the security reports in freebsd the amount of mails in
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the mailqueue hit me. After some further investigation I found even error
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messages of dspam, having trouble to rate spam for receivers which were not
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even in the system.
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To fix it, I read into the postfix documentation again, build new and hopefully
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better restrictions. The result was even more spam getting through.
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After a day went by and my head was relaxed I read the documentation again and
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found the following in the
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[postfix manual](http://www.postfix.org/VIRTUAL_README.html#in_virtual_other)
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> The `virtual_mailbox_maps` parameter specifies the lookup table with all valid
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> recipient addresses. The lookup result value is ignored by Postfix.
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So instead of one of the many restrictions a completely unrelated parameter is
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responsible for blocking mails for unknown users. Another parameter related is
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[`smtpd_reject_unlisted_recipient`](http://www.postfix.org/postconf.5.html#smtpd_reject_unlisted_recipient).
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This is the only other place I could find, which listed `virtual_mailbox_maps`
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and I only found it when looking for links for this blog entry.
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So if you ever have problems with receiving mails for unknown users, check
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`smtpd_reject_unlistef_recipient` and `virtual_mailbox_maps`.
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