Great!
If you still get (too) many Postmaster mails, usually aliased to root, they now accumulate in the /var/mail/root mailbox.
Frequent mails to root can mean a problem.
It makes sense to read them, and do some root-cause analysis.
Of course it's easy to truncate or delete the mailbox.
BTW I once wrote a Nagios plugin that reports file queues in /var (not only /var/mail/mqueue).
It can be run standalone on the command line.