Central function or class for sending email?

Is there a central mail class or function used to send all email? We're finding our server to be a little unreliable in terms of sending email, so we'd like to add some error checking and generally harden up the outgoing email process. Is there one block of code responsible for emailing, or am I going to need to hook the hardening measures onto individuals calls to mail()?

Thanks!

/includes/functions/functions_email.php handles all the email building/preparation.
/includes/classes/class.phpmailer.php handles all the communication with the mailserver
/includes/classes/class.smtp.php handles additional communication if using an smtp server.

v1.3.7 has some bugfixes included that may help with problems you're encountering with prior versions.

Thanks very much!