[Discuss] Migrating hundreds of mbox files to an IMAP server?

[richard.pieri at gmail.com (Rich Pieri)]

On Mon, 2 Jun 2025 07:32:30 -0700
Kent Borg <kentborg at borg.org> wrote:

> I've tried copying a big offline Thunderbird mailbox to a live
> Dovecot server, and it worked for the first 11,880 messages, but now
> won't do any more. I know Dovecot can handle more because this came
> from an earlier instance of Dovecot.

Dovecot can handle tens (maybe hundreds) of thousands of messages in a
mail folder. You don't specify which backend Dovecot is using: mbox or
Maildir. If you're using mbox then you may be hitting a timeout:
scanning the the mbox file takes longer than the server-side connection
timeout.

It's also well-known that Thunderbird doesn't scale. If you are already
using an IMAP server for mail storage then try something that works
better such as Alpine or Mutt or Claws-Mail.

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