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Mustafa Chelik
Asked: 2018-04-24 14:14:56 +0800 CST

Thunderbird can't connect to my mail server

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I have a fresh Ubuntu 16.04 server and I have to create mail server on it. I followed this tutorial that uses postfix & dovecot. Now I am able to sent email from server using mail command to my personal email but Thunderbird fails to connect and configure my created email. Email related processes seems working:

tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:993 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:995 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:110 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:143 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN

It could be because of my DNS entries. I'm not expert at these concepts. If you can help me, I'll appreciate it a lot.

P.S. ufw is disabled

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postfix

3 Answers

  1. Your mail server should listen on port 587 (submission) for user agents. This port should require STARTTLS and Authentication before accepting a message for delivery. Thunderbird works well with this setup.

    Thunderbird will try a few subdomains when it auto-configures. For the domain example.com, configure DNS for mail.example.com for the server running postfix and dovecot. (Replace example.com as required for your domain.) This should be an A record. Other names can be used such as imap.example.com, smtp.example.com and pop.example.com, but mail.example.com works for most protocols.

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  2. turns out I didn't uncomment smtp in /etc/postfix/master.cf file

    submission inet n       -       -       -       -       smtpd
  -o syslog_name=postfix/submission
  -o smtpd_tls_security_level=encrypt
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING

smtps     inet  n       -       -       -       -       smtpd
  -o syslog_name=postfix/smtps
  -o smtpd_tls_wrappermode=yes
  -o smtpd_sasl_auth_enable=yes
  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
  -o milter_macro_daemon_name=ORIGINATING
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  3. A lot of ISPs block outbound port 25 to stop people from spamming on their network. They only allow it to their own servers.

    You'd have to run postfix on a ssl enabled port and connect to that to send outgoing email

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