sending email fails

I'm using a leased linux server that uses cpanel and webhost manager.

I'm trying to set up email accounts and receiving is working just fine, but when I try to send, it isn't working at all. The way i'm setting up my account on thunderbird is

server name: mail.domain.com

port: 25 (also tried 26)

Security and Authentication: use name and password is checked. User name is user@domain.com.

use secure Connection: No

is there some setting in my WHM that I need to change to use my outgoing email

i've got my answer, I had to enable exim on another port