With a fully functioning linux-based email server (running postfix/Dovecot) how can one disable the ability to connect to SMTP/POP3/IMAP with external mail clients (or telnet, etc) while still (and only) using Roundcube webmail (that is, a local email service)?

Roundcube connects to Dovecot IMAP to retrieve its mail; and the server in general needs to communicate to the outside world, so simply shutting off the ports/firewall won't work to still be able to send/receive mail within the webmail application.

  • 2
    Are clients using SMTP/POP3/IMAP to retrieve mail or only HTTPS via Webmail? Dec 23, 2013 at 9:02

3 Answers 3


Just configure dovecot to listen on only for the sevices you don't want to expose to the outside, you can specify this in dovecot.conf.

imap_listen = localhost
imaps_listen = localhost

It's similar for pop3

pop3_listen = localhost
pop3s_listen = localhost
  • And there's a siminar inet_address = for postfix (SMTP)
    – mveroone
    Dec 26, 2013 at 10:02
  • 2
    Kwaio, you can only lock SMTP down the same way if you never want the system to receive email from external systems. The OP hasn't suggested that such is the case.
    – MadHatter
    Dec 26, 2013 at 10:43

Well you can use a firewall to ensure that connections to the imap & pop3 services cannot be made from outside the system. If your dovecot installation is on a different server then again, your firewall rules can be set up to allow connections to/from that system only.

As for SMTP, you can't just block this as you say. You can, however, make sure it only accepts connections to/from a separate smarthost that just acts as a mail relay, but this isn't ironclad by any means either. I think if you want to have any kind of server available on the Internet you have to accept that sooner or later people will find a way to connect to it in ways you hadn't anticipated, and rather than going gung-ho for preventing the impossible I would just do what was reasonable in this regard and then spend the rest of my energy on ensuring the system was securely configured and managed.


Much more effective is to limit connections from outer space for those who have passed authentication.

If the remote client knows a valid email/password and can establish TLS sessions on servers SMTP/IMAP - why not? As a side effect, your users can use native MUAs, built in IOS/Android.

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