Virus scan + removal on a mdbox mail storage

[Stuart Henderson]

On 2019-02-22, David Pottage via dovecot <dovecot at dovecot.org> wrote:
> On 2019-02-21 22:14, Christoph Haas via dovecot wrote:
>
>>>> NO! My mail storage is mdbox. And at the moment I have no intention 
>>>> to
>>>> convert it to Maildir!
>>> Could I ask why? maildir is a better storage format is almost every 
>>> respect.
>> 
>> well, I have a mailbox with about 50k emails ..., so one reason seems
>> to me better backup performance with mdbox, since there are much less
>> files to save.
>
> Assuming that you backup regularly then maildir is much better, because 
> new emails show up as new files, while old ones are left unchanged. This 
> means that an incremental backup only has to process new emails. With 
> mailbox, the file for the entire folder changes every time a new email 
> is delivered or the user edits any of them, so the whole mailbox needs 
> to be backed up again, resulting in far more I/O and time.

It sounds like perhaps you're confusing mdbox with mbox. mdbox uses
multiple files but not a single file per message. It is fairly sane for
backup handling - depending on how you set things up, you can have it
rotate after a fixed size, fixed time, or combination.

https://wiki2.dovecot.org/MailboxFormat/dbox