RT 4.4.1 is not sending mail

I'm trying to migrate RT 4.0.0 to 4.4.1. The installation, database migration
and LDAP auth is going ok, but 4.4.1 is not sending mail. I've enabled
outgoing email on tools/preferences and the aliases are already configured
as the old instance. It's not even registering the attempt to send mail on
the ticket. Does anyone have an idea? I'm using Centos 6.8.
That's my first RT installation/migration, so it can be a simple problem,
but i'm having many difficulties to see a solution. Thanks in advance.

The mail configuration in RT_SiteConfig.pm:
Set($MailCommand, "smtp");
Set($SendmailArguments,"-oi -t -ODeliveryMode=b -OErrorMode=q");
Set($SMTPServer, "<my-server>");
Set($SMTPDebug, 0);
Set($CorrespondAddress, "noreply\@<my-server>");
Set($CommentAddress, "noreply\@<my-server>");
Set($RTAddressRegexp , '^.*\@<my-server>$');




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