Tuesday, December 31, 2019

Some mailman list members don’t receive any mail

Still working on #3339.

It seems that the easiest way to reproduce our problem it to have our own mail server, i.e.postfix at LF does not use a relay. Because then we can at least see what happens. And this is what happens when I try to send something to any recipient @hot.ee:

Dec 30 04:39:52 myhostname-1 postfix/smtp[5611]: 1E78DAC52:
to=<lucsaffre@hot.ee>, relay=mx1.hot.ee[]:25, delay=6.2,
delays=0.02/0.05/6.1/0.1, dsn=4.3.2, status=deferred (host
mx1.hot.ee[] said: 450 4.3.2 Service currently unavailable (in
reply to RCPT TO command))

The system admin of hot.ee thinks that maybe I am greylisted and suggests that I increase my timeout, iow to be more patient when waiting for their answer.

As explained here:

# Message delivery time stamps
# delays=a/b/c/d, where
#   a = time before queue manager, including message transmission
#   b = time in queue manager
#   c = connection setup including DNS, HELO and TLS;
#   d = message transmission time.

So the “connection setup including DNS, HELO and TLS” took 6.1 seconds. I looked for configuration settings that might instruct postscript to stop waiting:

$ sudo postconf | grep timeout
connection_cache_protocol_timeout = 5s
lmtp_connect_timeout = 0s
postscreen_upstream_proxy_timeout = 5s
smtpd_upstream_proxy_timeout = 5s
# (showing only entries with less than 10s)

I looked up the meaning of those settings in the docs but could not find anything that looks worth a test.

I verified that our server is not listed at spamhaus: