Outbound SMTP to secureserver.net?

[ADB100]

I have a 'virgin' install of FreePBX and I am using it purely as a SIP-to-SIP gateway sat between a Cisco CUCM 7.1 server and the Internet where my SIP provider is. Asterisk is being used as CUCM doesn't perform SIP registration. This is all for testing.
In my NetFlow logs from my Internet facing router I can see the server sending traffic. I can see the SIP signalling and the RTP/RTCP traffic which is what I am expecting. I can also see some stuff I am not sure about. This is SMTP to 72.167.238.201 & 216.69.186.201, both of these resolve to secureserver.net. I have checked on the Asterisk server and it appears 'postfix' is running and is trying to send SMTP mail.
Obviously I can block this traffic on my firewall or stop the service on the server but I am not sure whether its needed? The postfix logs show that mail isn't being sent as my source IP is not trusted. I have my own mail server so can I reconfigure it to send here?

Andy

 

[busster]

I know there is a field under general settings for an email address to advise you of upgrades.

Not sure why other emails would be sent.

 

[ADB100]

I think its the underlying Centos operating system. It seems to try to make an SMTP connection to the local domain name, this fails a few times and then it attempts to send mail via smtp.secureserver.net and this also fails.
I disabled it with

chkconfig postfix off

and it hasn't happened since.
I am just unsure whether Asterisk needs it for any reason?

Andy