[Dovecot] removing uid, index and cache files

Since a couple of days we're facing a problem with dovecot/MUA and multiple appeareances of single mails. The mail is physical existant only once but outlook shows it twice or more times. Then after some minutes these multiple "virtual" mails just disappear. Because this happens with different MUAs (Outlook and Thunderbid) I assume dovecot causes the problem.

All mail are received by »getmail« from outside via POP3 and delivered to the users local Maildir. This was working without problems for over a year now.

Is it save to remove to following files (will dovecot rebuild them) from every users Maildir?

dovecot.index dovecot.index.cache dovecot.index.log dovecot.index.log.2 dovecot-uidlist

Thahks in advance, Lars