[Dovecot] mdbox - healthy rotation size vs default

[Javier de Miguel Rodríguez]

Another intesting thing for this thread: if you set a very high
value for mdbox rotate settings, your incremental backups will be awful.
If you have hundreds of messages in a mdbox and you doveadm purge one of
them, the full .m file must be copied in the incremental / diferential
backup. 

I use 10 MB+zlib for "main storage" and 250 MB+bzip2 for
alternate storage. 

Regards 

Javier