[Dovecot] How to remove duplicate GUID messages from storage?

[Daniel Parthey]

Hi,

I tried to import messages like this:
doveadm import -u username at example.org mdbox:/mail/dovecot/example.org/username/mail mbox:/root/mail.txt all

This seemed to have imported the same messages in the mail storage,
as they were already there. And now I have got a lot of duplicates.

Then I deleted the mbox:/root/mail mail stuff from "mailboxes" folder
and the storage remained, with duplicate GUIDs.

The following command
doveadm -v force-resync -u username at example.org INBOX
outputs lots of messages like this one, with different GUID
doveadm(username at example.org): Error: mdbox /mail/dovecot/example.org/username/mail/storage: Duplicate GUID 0b8a032d66a0924fb42c0000de5f8128 in m.55:45484041 and m.14:52173045

The messages at m.55:45484041 and m.14:52173045 have the same content,
since they were seemingly imported from the mail store itself,
they are in the storage twice now and require twice as much disk
space as before.

How can I manually remove these identical, duplicate messages
from the storage to save space? Dovecot does not do it
automatically.

Kind regards,
Daniel