Mailscanner UDP connections

[Jeremy Henty]

Running lsof on a Mailscanner box (an ancient RH7) I see every few seconds a batch 
of entries like this:

MailScann 19062 postfix    7u  IPv4 22883898       UDP *:58004 
MailScann 19062 postfix    9u  IPv4 22883899       UDP *:58005 
MailScann 19062 postfix   10u  IPv4 22883900       UDP *:58006 
MailScann 19062 postfix   11u  IPv4 22883901       UDP *:58007 
MailScann 19062 postfix   12u  IPv4 22883902       UDP *:58008 
MailScann 19062 postfix   13u  IPv4 22883903       UDP *:58009 
MailScann 19062 postfix   14u  IPv4 22883904       UDP *:58010 
MailScann 19062 postfix   15u  IPv4 22883905       UDP *:58011 
MailScann 19062 postfix   16u  IPv4 22883906       UDP *:58012 
MailScann 19062 postfix   17u  IPv4 22883907       UDP *:58013 

What is Mailscanner doing that requires these connections?  RBL checks?

Regards, 

Jeremy Henty