Via SMTP relay/smarthost (min. OTRS 1.1)

OTRS is able to send out emails via SMTP ( Simple Mail Transfer Protocol / RFC 821). Mostly used on non unix platforms (e. g. win32).

There are the following config options for Kernel/Config.pm:
    # SendmailModule
    $Self->{'SendmailModule'} = 'Kernel::System::Email::SMTP';
    $Self->{'SendmailModule::Host'} = 'mail.example.com';
    $Self->{'SendmailModule::AuthUser'} = '';
    $Self->{'SendmailModule::AuthPassword'} = '';