MAIL...port settings

A friend is having problems getting his MAIL program set up. He can receive but he can't send email.

tech support from the IP that hosts his email says he needs to change the Port settings for his outgoing email and has given him the number to use. They've also given him a different port number to use for his incoming.

In MAIL preferences we've only found one place to enter a Port number. If he changes that number to the Port number they want him to use, then his incoming email stops working and he still can't send email.........is there a second place to enter the port number in MAIL preferences?

Any ideas as to what might be happening? or things to try to fix it?

he's using a version of OS 10.5 if that helps.

 

he has something like 5 email addresses he's trying to set up. 3 are thru the IP that hosts his small web site and provides email. The other 2 are through other people's web sites where he's been given email addresses. None are yahoo or gmail. None of the 5 email accounts will send, even those 2 that are through the other peoples' web sites. All of the accounts receive email though.

He's talked to tech support for at his site host to confirm the incoming and outgoing mail servers (we believe those are correctly set)