OutBound SMTP Server Mail issue

Hi all

I have a Live SMTP server for outbound mails ( Mail being sent from my organization to outside domains).
A large chunk of mails are not being sent and reside in /var/spool/mqueue directory.

The header of there mails are:

From: Mail Delivery Subsystem <MAILER-DAEMON>

How can I configure my SMTP server to flush out these unsent mails using either SMTP's own settings or by using procmail ?

The mail queue is continuously increasing due to these unsent mails and is causing a headache.

Regards