SMTP and Sendmail! HELP!

[Vellor]

SMF Version: SMF 1.0.7
I dont know how to make the SMTP work or the Sandmail work. so i need your help please!
when some one are register it comes:

An Error Has Occurred!

mail() [function.mail]: Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() 

Please i realy need your help.

[xenovanis]

I think you need to contact your host about this.