[Dovecot] reason to switch to 1.1

[Cor Bosman]

> How large are the (individual) mailboxes you're hosting there?

Most of them are max 500MB, but average use is much less. It's a little
difficult to calculate because almost all POP users empty their mailbox.
We did some reports a few months ago where it showed that average mailbox
size for POP users is less than 5MB, while average mailbox usage for
IMAP was over 50MB.  

Cor