[cobalt-users] Mailq - Total Requests: 330 - what's happening?

["Leo B." <lbaghdassarian@xxxxxxxxxx>]

A few minutes ago, I received an admin email stating "The CPU is heavily
loaded." A minute after that I received an email stating "the SMTP (mail)
server is not responding."

I restarted the email server via the control panel web admin.  And that
temporarily took care of the problem.  It came back within a few minutes.
This has happened before, and I remember it having to do with a mailq
overload.  Currently, when I run "mailq" via SSH, I get a long list of mails
(at the end it shows: Total Requests: 330).  From the items I can scroll up
and see, they all seem to be caused by the same problematic email address:

hADNG5k32608     7796 Thu Nov 13 15:16 owner-list@xxxxxxxxxxxxxxxx
                 (Deferred: Connection timed out with isp.net.)
                                       user@xxxxxxx

Above is an example with the list name and email address changed for posting
purposes...

We have a few lists on our RaQ that are pretty active... It looks as if this
email address is causing a lot of problems.  But before trying to figure out
that issue, how should I proceed cleaning this up?  Is there a way to run
mailq and have it scroll screen by screen (not all at once), so I can verify
this one email address is causing all the problems?

Mqueue q1, q2, q3, q4 seem full (there are a bunch of items in all of them).
I know I can probably just delete them all, however, there may be other
items in there that are important, right?  Is there any way to delete only
the email for "user@xxxxxxx" and not mess with other mail?

Would items in the mail queue only be from people using the RaQ as an SMTP
server?  We don't encourage/allow smtp usage of our raq... So would it make
sense if I assumed ALL those mails in the mqueue are because of list
activity?

And finally, does anyone know why this is happening?  Can there be some loop
error that is not just dumping these emails that are being 'deferred?'  Is
our system being used by someone else (hacker, etc.)?

I really wish I knew more about linux, logs, email, etc... But
unfortunately, my knowledge here is not too extensive.

Any help is of course very appreciated.

Thank you,
Leo