Customer forgotten password email not sent [SOLVED]

Hi Guys
Hopefully you can help me out here.
Basically, when a customer goes through the forgotten password process, they are not receiving the email with the new password.

The client has got me to change the MX servers for the email.
Instead of being managed by the web server, they are managed through smtp.somethingsecret.com

Would i be right in assuming that I need to set up the Mail Protocol in Settings to use the Smtp host, username, port etc?
If that is the case, do i need to change anything anywhere else?

Thanks

webecho

OC 1.5.1.3
Server Apache

As a follow up, I've also tried sending mail from the Mail section in Sales - these don't work either.
So there's no mail being sent by OC through the server.

I've found another 4 threads with exactly the same problem and no solution.

Anyone from OC looking at this?

webecho

Just to say, this all turned out to be because my server had disallowed sending emails to external email addresses!!!
Ridiculous I know.