I have setup email server for small company whit Ubuntu 16.04, Postfix, (virtual users) Dovecot, Amavis-new, Sieve for Junk mail moving to Junk folder and fetchmail whit fast fetch time (4sec). Two months so far so good, working just fine. Two weeks ago I checked logs as usual for error, spamfilter activity, hackers activity etc and I noticed this error:
Nov 18 16:37:12 server dovecot: imap(mail@server.com): Error: Corrupted index cache file /var/mail/vhosts/server.com/mail/dovecot.index.cache: Broken MIME parts for mail UID 420 in mailbox INBOX: Cached MIME parts don't match message during parsing: Cached header size mismatch (parts=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)
(Mail address is changed of course)
Today I checked again and got this error again. Far as I have discovered is that this might be Dovecot bug whit Sieve. Do anyone have experience whit this? Can this result in mail corruption? I have found cases where email client is causing it. Far as I know Outlook (I don't know version) and iphone is used.