[Koha] Configuring smtp mail server to work with Koha

Hello,

I want to configure an smtp server so that Koha can use it to send e-mail
notifications.
I was expecting some sort of configuration file where I would configure the
server, username, password and some other parameters but that is not the
case.

>From my research I found 2 possible ways:
1) Editting /usr/share/perl5/Mail/Sendmail.pm file and inserting the smtp
server at the top of the file, but where do I insert the smtp credentials
(user/pass) in that same file? or
2) Through some postfix configuration which I really would like to avoid.

Would anyone shed some light on the matter or provide some sort of
guidelines on how to do this?

Thank you very much,

Pedro Amorim