Hi list.
A couple of months ago an email I sent from my phone was bounced by the
recipient's SMTP server because the email had no Message-ID header. It
turns out the email app that I've been using on my phone for years
doesn't generate a Message-ID, but this was the first time that this had
been a problem...
Anyway it turned out to be fairly simple to get Postfix to add the
missing Message-ID header: I just needed the email to satisfy
"local_header_rewrite_clients".
But this got me thinking about 'best practice' configuration of Postfix
to meet RFC 6409, and I realised that (AFAICT) this isn't covered by the
Postfix documentation. And so I assume that most people (like me) just
uncomment the submission lines (in master.cf) provided by their distro's
postfix package? But this Message-ID experience has shown me that the
distro's master.cf submission, while good, is not 100% perfect?
And so I wonder whether it might be worthwhile to add a page to the
Postfix documentation to describe how to correctly configure Postfix
submission/submissions services?
FWIW in case anyone is interested in my solution to the Message-ID
issue... My initial solution was to specify (in main.cf)
"local_header_rewrite_clients = permit_inet_interfaces,
permit_sasl_authenticated". And while this did the trick, it didn't feel
right, because it relied on the indirection - i.e. submission requires
SASL authentication which therefore makes it eligible for header
rewrites. What I really wanted was to say that submission is eligible
for header rewrites period. And so I ended up removing the option from
main.cf and including "-o local_header_rewrite_clients=static:all" in
master.cf instead:
submission inet n - y - - smtpd
-o syslog_name=postfix/submission
-o smtpd_tls_security_level=encrypt
-o smtpd_sasl_auth_enable=yes
-o smtpd_tls_auth_only=yes
-o smtpd_reject_unlisted_recipient=no
-o smtpd_delay_reject=no
-o smtpd_client_restrictions=$mua_client_restrictions
-o smtpd_helo_restrictions=$mua_helo_restrictions
-o smtpd_sender_restrictions=$mua_sender_restrictions
-o smtpd_recipient_restrictions=
-o smtpd_relay_restrictions=permit_sasl_authenticated,reject
-o milter_macro_daemon_name=ORIGINATING
*-o local_header_rewrite_clients=static:all*
FYI "-o smtpd_delay_reject=no" above is another manual addition of mine,
not part of original distro's master.cf.
Thanks,
Nick.
