Check for large mailboxes in Exim

[dima]

> On my mail server how can I check the sizes of the mail boxes or the
> mailboxes larger than 1 mb 
You should mention the mailbox format used.
Let's consider you use the same format as I do (Mailbox). My boxes are under the /var/spool/vmail/ directory. The directory structure is like the following:
/var/spool/vmail/<domain>/<box>
So I type:
# du -k -d 1 /var/spool/vmail/*
& get the strings like:
33900 /var/spool/vmail/<domain_1>
210   /var/spool/vmail/<domain_1>/<box_1>
2082  /var/spool/vmail/<domain_1>/<box_2>
....
The sizes are in kilobytes by default.
You can easily parse the stuff with text utils for your application.