Best practices for backing up small mailserver to remote location

[Joseph Tam]

On Wed, 8 Aug 2018, daniel_1983 at protonmail.com wrote:

>> -   rsync
>
> may not be the best option depending on the format of mailboxes.  If
> you're using maildir or maildir+ that's fine, but what about mbox or
> dbox ?

It depends on the situation.  I can't speak for dbox, but if the mbox
file is not updated, then it's no different than maildir.  (It might
actually be slightly faster as you don't read a lot of metadata for
boxes with many messages.  This is a consideration for Maildir if the
filesystem format handles metadata poorly.)

For mbox where most of the updates occur at the end of the file (i.e.
the latest messages), then you'll have to incur read I/O at the source
to calculate rolling checksums, but only the changed blocks will be
transferred.

The worst situation is a modification at the beginning of a large mbox
(e.g. delete first message), which will trigger a full copy.

So for mostly static mboxes, and moderately sized active mailboxes,
rsync will work fine, especially owing to its simplicity.

Joseph Tam <jtam.home at gmail.com>