Amedeo, > Weird 'Bad sender address syntax', where '""@' come from ? some > ideas? (see info below)
Ok.. I've investigated a little and it come out that my postfix is accepting email addresses with an empty local-part. The postfix 'strict_rfc821_envelopes' configuration parameter handles also this behaviour.. (default: disabled). Amavis don't love it too much ( ""@domain.tld ) and "gracefully" stuck .. with a probable DoS risk. So, my fault.. I wasn't aware of this requirement (strict_rfc821_envelopes=yes).
It's a case of 'garbage-in/garbage-out'. Neither a null local part nor a "" are valid, but Postfix chose to mercifully permit the first but not the second, unless strict_rfc821_envelopes=yes. RFC 5322 requires quoting of a local part which is not following a dot-atom syntax, which is what amavisd did, at least until version 2.4.0: amavisd-new-2.4.0 release notes - no longer bother to convert addresses like <""@yahoo.com> to <@yahoo.com>, both forms are invalid anyway, and recent versions of Postfix treat them the same. It is probably a good idea to set strict_rfc821_envelopes=yes in main.cf to reject such non-replyable sender addresses straight away, otherwise we end up processing such mail with inability to bounce it when needed, effectively losing it; Mark
