[KLUG Members] SMTP 452 deferred?

[Bruce Smith]

I'm getting complaints that we are having problems sending email to a
business in Canada, who we typically exchange a lot of email.  The mail
log at my end is showing a ton of 452 deferred errors at their end.

Anyone know anything about a 452?  I get the impression from my
google'ing that their SMTP server is overloaded.  Is that correct?

Some of the messages in my log also seem to support the overload theory:

 stat=Deferred: 452 #4.3.1 queue full - on relay of: MAIL From:
 stat=Deferred: 452 #4.3.1 out of RAM - on relay of: MAIL From:

I'm also getting a lot of 451 deferred errors.

A whois lookup shows their mail is being hosted by bellnet.ca 
"Bell Canada the largest Canadian telecommunications operating
company ..."

The good news (for me) is the problem appears to be on their end and not
mine.  But now I'm being ask to lend them some advice on how to fix the
problem at their end.  Anything useful I can tell them, other than "get
someone else to host your email"?  (I'm talking to the small end-user
company, not Bell Canada! :)

 - BS