First, you need to make sure that the message is not still in the mail queue.
Use
mailq to see what if anything is in the queue.
Also, Exim makes some very good logs. Check the mail logs and it should show when it got the message to send, what results it got when it tried to send as well.
Also, you can use an Exim command to see what it will do with an address like:
exim -v -bt
xxx@uthandosa.org
It should show you where it will try to deliver the message and the MX records if any found for the mail host that accepts email for that email.
Like:
Code:
wk3dd@ulterius:/etc/munin# exim -v -bt xxx@uthandosa.org
xxx@uthandosa.org
router = dnslookup_dkim, transport = remote_smtp_dkim
host xavier.macrolan.co.za [41.222.227.20] MX=0