Book:OTRS 3.0 - Admin Manual/Chapter 7/1

Via Sendmail (default)
OTRS can send out emails via Sendmail, Postfix, Qmail or Exim). The default configuration is to use Sendmail and should work out-of-the-box.

You can configure the sendmail settings via the graphical configuration frontend (Framework::Core::Sendmail)

Via SMTP server or smarthost
OTRS can send emails via SMTP (Simple Mail Transfer Protocol / RFC 821) or Secure SMTP. You will want to use this on non-UNIX platforms (e.g. Windows).

The SMTP server settings can be configured via the SysConfig (Framework::Core::Sendmail). If you don't see SMTPS available as an option, the required Perl modules are missing. In that case, please refer to "Installation of Perl modules required for OTRS" for instructions.