[BlueOnyx:15184] Mail not being received on 5108R

[Adam Lepp]

For the last 4 hours, my server has been unable to receive email from some
senders.
e.g., sending from AOL produces the error message:  

"Action: failed
Status: 4.4.2
Diagnostic-Code: X-Outbound-Mail-Relay; conversation with
    mail.XXX.com[AA.BB.CC.DD] timed out while sending end of data --
    message may be sent more than once"

I test the server with WebSitePulse, and have received this failure message:

"4.3.2 Please try again later"

I am able to receive from some senders, but messages tend to be delayed.
My "mqueue" currently has 100+ messages.

I restarted sendmail and spamass-milter multiple times, and restarted the
server twice.
In reading about similar issues, it appears to be related to Spam Assassin,
but I haven't been able to find a solution.
I haven't changed anything on the server other than the YUM adjustment from
last week (Thanks Michael)

This occurred out of the blue - server load and disk space are fine. 
It does take a rather long amount of time to log into SSH -- perhaps this is
related.
Once I'm in, it's fast, and "su -" logs me in as root in the normal, quick
time.

I added an additional email address just to make sure I receive list
postings.

Assistance would be greatly appreciated.

--- Adam