Ion Auth - Lightweight Auth System based on Redux Auth 2

[eluser]Keloo[/eluser]
Ok so I've used the library from the "master" branch from git, and I've got a problem when trying to register.

I've enabled email_activation and I get an error:

A PHP Error was encountered

Severity: Warning

Message: 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()

Filename: libraries/Email.php

Line Number: 1553

What should I do to fix this problem ?