We use messagelabs for our mail filtering/spam/av, so all incoming mail is
from there servers, and all GWIA mail sends out via. their servers. So GWIA
is set to relay to messagelabs.

If our router or ISP link is down, and you send an email, we get mails
bouncing back immedietly. I don't know if this is a new problem, because it
has only just started happening? Our links are DSL so are subject to the odd
outage, which if you are unfortunate enough to be sending an email at the
time, will result in this "Message Status - Undeliverable" failure message.

Can it be setup to queue and retry the outbound host if it cant resolve it
first time?

Thanks in advance, Alan