[Dovecot] Random questions on backing up Dovecot

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Hi, I've read a few threads about the subject, but I am hoping someone can
comment on a few misunderstandings that I might have? It seems like doing a
tar of the mail folder location then rsyncing it over to the backup
location is the general idea.

I plan to have dovecot create 6 virtual users using Maildir, located at
/var/mail.

A few specifics I am unclear on:


1)
Someone here gave a descriptive outline on this here:
http://www.dovecot.org/list/dovecot/2011-August/060368.html

It's a bit silly, but does anyone have any comments about his suggestion on
doing a 'tar cvf' first, then doing a gzip on that archive? Are the
benefits really that great?

2)
My lack of understanding of control files and index files contribute to
this question. If I want to move to a new server and I only tar'd my
/var/mail,
how does this affect control files? Is it as simple as just copying pasting
back into /var/mail on the new server, and then Dovecot will create new
UUIDs for the messages?

3)
How do I handle the case where the script is currently tarring/gzipping the
entire /var/mail, but I receive a new mail during that period? What happens
if I use thunderbird to delete a mail during the archiving process?