The IANA port allocated for ManageSieve is 4190/tcp, and the old port used by timsieved and other managesieve software in many distros (2000/tcp) is allocated for Cisco SCCP usage, according to the IANA registry.

Starting with the version 4.38 of the Debian “netbase” package, the “sieve” service will be moved from port 2000 to port 4190 in the /etc/services file. This affects to those using Debian Squeeze, and Debian Sid. Debian Etch and Debian Lenny users are NOT affected.

Any installs which used the “sieve” service name instead of a numeric port number will switch to the new port number as soon as the services are restarted/reloaded, and in some cases, immediately after /etc/services is updated.

This will affect Cyrus IMAP. This may also affect other sieve-enabled software such as DoveCot.

In order to avoid downtime problems, mail cluster administrators using Debian are urged to verify their Cyrus (and probably also DoveCot) installs, and take measures to avoid services moving from port 2000/tcp to port 4190/tcp by surprise in either servers or clients.

It is worth noting that:

  1. /etc/services will only be automatically updated if you never made any modifications to it. Otherwise, you will be presented with a prompt by ucf or dpkg asking you about the changes.
  2. You can edit /etc/services and change the sieve port back to 2000 if you want (this is not recommended, though).
  3. You can edit /etc/cyrus.conf and any other relevant config files for your mail/webmail cluster (e.g. on the sieve web frontends) ahead of time to force them all to a static port number.
  4. You can configure cyrus master to listen on *both* ports (2000 and 4190) at the same time, and thus avoid the problem entirely. This also allows for a much more smooth migration from port 2000 to port 4190.

Contributed by: Henrique de Moraes Holschuh