migrating from maildir to mdbox, preserving pop3 UIDL
I'm trying to migrate from maildir to mdbox while preserving the pop3 UIDL (and the imap UID).
The problem is, for maildir we use (for compatiblity with qpopper):
pop3_uidl_format = %f
Problem is, as soon as I convert that to mdbox, then whenever a client issues the UIDL command via a POP connection, the connection is closed and this error is displayed in the log:
Error: UIDL: File name not found (pop3_uidl_format=%f not supported by storage?)
As a workaround, I enabled "pop3_reuse_xuidl = yes", and before conversion I put an X-UIDL: header in the mails. However, since the UIDL is the filename and the filename also contains S=<size>,W=<sizeOnWire>, I need to change the header in such a way that the size and number of lines stay the same. That's... tedious and error-prone.
Is there an easier solution, eg teaching 'doveadm sync' to preserve pop3 UIDL somehow?
For the record, I currently convert maildir to mdbox using: