Mailer problems

Hi, I am new to PunBB but I am involved in a forum which uses PunBB.  I am not sure if this mailer problem is even related to PunBB so if not then I am sorry for wasting your time.

I would like to E-mail everyone in the database on my Sql but am having some problems.  I go to Administration and then mailer (under plugins) so far everything is fine, I write the message (and title it) and click send.  The mailer plugin "finds" all the e-mails in the Sql (thanks to some help from a friend, as before it would not even find the e-mails).  After the mailer has finished sending the 5k e-mails (or however many) I realise that nobody has received any of the e-mails.

I am not sure what to do or where to go from here.  The guy who fixed the "looking up the e-mail address'" part has mentioned that there could be a problem with the Port??? or something.

Any ideas would be great, if you want me to post what's in the mailer file or anything then let me know, I really need some help with this and would really appreciate any help that can be given.

Thank you,

L_O_Z