Exim 4.69 denying outbound mail due to syntactically invalid EHLO (bizarre pseudo-MAC FQDN)

Solution 1:

Looks like someone somehow didn't set a computer name for their Mac. Try having the client set a computer name by going to System Preferences then Sharing.

Solution 2:

Read message #24 on http://business.forums.bt.com/t5/Email/email-on-Mac-problem-sending/td-p/46630/page/3. Message #26 also has a slightly easier test/fix, where he says:

change the 'Computer Name' to have only letters and numbers - no spaces or punctuation/special characters

e.g. I had "Ian's MacBook Air" and changed to "iansmacbookair"

REBOOT the mac

SMTP will burst into life

Then he says you can change it back to whatever you want because the router only attempts to resolve the hostname once. He did not state whether this survived a router power cycle, but I bet it does not, so you would have to repeat every time the router was power cycled. To me the question #24 is the better, more proper, long term fix.