Outlook 2011 error 5.5.2

I have just installed Office 2011 on my MacBook. Am trying to create mail merge documents on Word, sending to Outlook. AOL is my ISP. The emails (I've only tried 2 as tests so far) get hung up in the Outbox and I get the error message: 5.5.2 Recipient address rejected: need fully-qualified address.

What do I need to do? Thanks!

This is normally attributable to a mal-formed email address or to the config of the mail server - in your case it's AOLs server.

Can you send a "manual" email to the problem address?

Yes, outgoing individual messages work fine.