Paste your Mozilla rule file here (msgFilterRules.dat in your IMAP directory):

Use '/' instead of '.' as IMAP folder seperators
e.g. configured "unixhierarchysep: yes" in /etc/imapd.conf when using cyrus IMAPD

Write sieve rules as one single statement rather than a series of seperate if blocks.

Add stop command to the end of each converted ruleset.