[Dovecot] Bad creation timestamp of migrated mails (maildir format)?

[Lukas Weiß]

Hello everybody, 

ive just switched to dovecot imap because dbmail
i used before is not developed any further and sql storage is difficult
to backup. Ive done that, by setting up dovecot with maildir format and
copy mails from old dbmail to new dovecot imap server with my mail
client (thunderbird). 

Unfortunately migrating to dovecot brought me
some problems with my Android K9 Mail client: Sync with IMAP-Server
shows me only the oldest mails. 

I think the problem is, that K9 only
fetches the newest mails (25) from the server (to save memory etc).
Which mail is "new" is probably determined by creation timestamp of the
email-files in my mailbox, which was copied newest first on migration
from dbmail to dovecot. So the older mails have the newer creation
timestamp on file system. 

Do you have any suggestions how to fix that
problem? Maybe migrate to dbox mailbox format? 

BTW: New mails show up
correctly, as the creation timestamp is new. 

Thanks 

Lukas