Telnet to SMTP gets no 220 response unless user is specified

Question

My server is setup to generate outgoing email only (no receiving), and is timing out when attempting to contact smtp.example.com

Essentially the email is generated by a process on myserver.example.com, sent to postfix on the localhost, which acts as a satellite system and relays the email to smtp.example.com

Error messages from postfix on myserver.example.com are:

Date/time-stamp myserver postfix/smtp[####]: ##########: to=<[email protected]>, relay=smtp.example.com:25 delay=1029, delays=729/0.01/300/0, dsn=4.4.2 status=deferred (conversation with smtp.example.com timed out while receiving the initial server greeting)

And this is the same error regardless of the recipient. Outbound emails are queuing up and never getting sent.

I've confirmed this timing-out by telnet smtp.example.com 25 and finding that I don't even get the initial 220 response from the SMTP server.

However, if I telnet -l myuser smtp.example.com 25 instead, I receive the 220 response immediately and I can send an email as expected.

I've configured postfix to use SMTP-AUTH by adding the following entries to main.cf

relayhost = smtp.example.com
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/password
smtp_sasl_security_options = noanonymous
smtp_connect_timeout = 120s

Can anyone suggest how I might change my postfix configuration to get the type of speedy (or any) response I get by using telnet -l myuser?

Solution

SMTP is not able to understand the user that you set with -l, because its another protocol than telnet.

I would guess that by specifying -l your telnet client is automatically posting some stuff into the smtpd and the output that you see then is just what it responds to any random input?

But anyway. If you just telnet to your smtpd's port 25 and get no output at all, then there should probably be some error in the logs right at the time when you connect. Maybe you should try checking the logs with tail -f while connecting? depending on your distro the logs might be in different files, for example on SuSE it would be:

tail -f /var/log/mail.info /var/log/mail.err /var/log/mail.warn

Now while you run this tail, connect to the smtpd the same time, to see if some errors are written into the log.

Comments

[Jenny D]

Do a tcpdump for all traffic to smtp.example.com when you do a regular telnet as well as a telnet -l and see what the difference is.