Newsletter Sending Issues

[CheekyCockney]

Tried sending my first newsletter today and got the following message.

Email Error: Could not instantiate mail function. Please check Admin->Configuration->Email Options->Email Transport.

I have found the following thread which i plan to work through to fix the problem.
http://www.zen-cart.com/forum/showthread.php?t=59041

BUT

I have sent numerous tests to the test group and they have worked everytime. Also, on this first mass email attempt it appears to have sent 53 out of what should have been 66 emails before the error message appeared. That is, there are 53 green ticks with the error message underneath. Could it send some and then suddenly stop? Do you think these have sent at all?

Any thoughts? Thanks in advance.

[DrByte]

Yes, it sent the ones it mentioned. It must be croaking on a bad address.

[CheekyCockney]

Croaking eh, is that a technical term?! Ha, thanks for the info, I was able to check with someone and yes it appears they did send. It looks like a '.co_uk' caused the issue.

Cheers!