Accidentally deleted .imap folder, how can I reindex?

[Les]

Hello,

I have several users with Maildir format. After upgrading from 2.2 to 2.3,
some directories could not be opened from thunderbird. The server log shows
all kinds of errors including these:

Corrupted record in index cache file
/home/user01/Maildir/.Elk&APw-ld&APY-tt/dovecot.index.cache: UID 2802:
Broken physical size in mailbox
Cached message size larger than expected (18 > 17, box=Sent, UID=2802)

While trying to fix the problem, I have accidentally deleted some of the
index/cache directories. In particular, Maildir/.Sent/.imap and
Maildir/.Sent/cur/.imap folders were deleted, but all of the mail message
files are there. When I try to open the "Sent" folder from thunderbird, it
does not show all of the messages. It only shows messages until 2019.01.12.
If I send out an email from thunderbird, then a new message is copied into
the Maildir/.Sent/ folder, but it is not visible from thunderbird. I have
already tried to unsubscribe + subscribe to the Sent folder, but it did not
work - it re-downloads all messages until 2019.01.12, but not after that.

Can I somehow regenerate the index files, force dovecot to recreated .imap
foder, and force thunderbird to re-download and show all of the files
somehow?

Thank you,

   Laszlo
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