courier-dovecot-migrate.pl, imap headers are reloaded after migration

Question

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Hello!

Migrating from Courier to Dovecot 2. After running the script, Thunderbird still downloads the headers again.
Who knows what's the matter?
The script was taken from the official wiki.

Help me please.

Answer 1

"Downloads the headers again" - means the POP3 protocol.
When POP3 connects, the client stores the database of letters on its own (or only the headers, as configured), while indexing goes according to the message number on the server. When the server changed, the numbering also changed, respectively, the client considers that the letters are new, since there are no such numbers in the local database.
The usual practice is to use IMAP access - when letters are stored on the server (and many other goodies, compared to POP3) - this greatly simplifies migration.