Description of problem:
When the dovecot service starts, it sometimes fails because RPC is using one of the ports dovecot uses (in our case imaps, 993).

Dovecot should use the portreserve facility to reserve ports for imap, pop and lmtp.

This is a matter of installing a file in /etc/portreserve containing
imap imaps pop3 pop3s lmtp

and running something like

        # tell portreserve to release the port
        [ -x /sbin/portrelease ] && /sbin/portrelease dovecot &>/dev/null || :

in the start section of the script.

Version-Release number of selected component (if applicable):
dovecot-2.0.9-2.el6_1.1.x86_64

How reproducible:
Sometimes

Steps to Reproduce:
1. Reboot system using nfs / nis

Actual results:
Dovecot service fails to start

Expected results:
Dovecot service should always start

Additional info: