I'm migrating from Courier-IMAP. On first access of folders I get this log (slightly anonymized):

Jan 1 18:38:27 mail dovecot: imap(username): Error: Cached message size smaller than expected (1452 < 1668) Jan 1 18:38:27 mail dovecot: imap(username): Error: Maildir filename has wrong S value, renamed the file from /var/vpopmail/domains/domain/username/.maildir/cur/1206559119.14350.mail,S=1452:2,RS to /var/vpopmail/domains/domain/username/.maildir/cur/1206559119.14350.mail,S=1668:2,RS Jan 1 18:38:27 mail dovecot: imap(username): Error: Corrupted index cache file /var/vpopmail/domains/domain/username/.maildir/dovecot.index.cache: Broken physical size for mail UID 161 Jan 1 18:38:27 mail dovecot: imap(username): Error: read(/var/vpopmail/domains/domain/username/.maildir/cur/1206559119.14350.mail,S=1452:2,RS) failed: Invalid argument Jan 1 18:38:27 mail dovecot: imap(username): Disconnected: Internal error occurred. Refer to server log for more information. [2014-01-01 18:38:27] in=135 out=63515

This is the same in 2.2.6 and 2.2.10.

Greetings,

Eike