This might be helpful to some people:

I take care of two forums. On one there was a change of Admin. Recently the mail relay was actively refused by the host server. This was investigated but the Support team could not find the cause; it worked on their end. It also worked on the other forum and I thought it was down to the .INI file for the first forum.

Later however, when the problem was raised about mass mailouts being refused I found that the Admin email address on the board was a personal one - by this I mean "someone" at yahoo.co.uk

I set up an in-site address "someone at "url" (set up a redirect) and it worked fine.

The reason for this problem is that WHB took the step to stop misuse of the email system by only allowing emails to generate/finalise if the Admin email is within their host. Thus me@mysite.com will work, me@hotmail.com will not work.

Simple when you know how.

M