To disable SSLv3 for imap within the dovecot package:
Create or update the local.conf file in /etc/dovecot like this
ssl_protocols = !SSLv2 !SSLv3
and test the result
openssl s_client -connect mail.example.com:993 -ssl3
which now shouldn't be able to connect to your imap server. That is the right reaction, now you are protected agains that Poodle attack.