Mail URL Filter blocked our email - why?

Question

Mail server

We set up maximum acceptance and friendliness for the emails we send out. About 1 time per week we do a newsletter exclusively for subscribed customers!
Recently one of our clients sent us a message like this:

Your email triggered a mail filter:
Scanner(s): Mail URL Filter
Context(s): unknown
Detection(s): unknown
Source IP Address: XX.XXX.XXX.XX
Source Host Name: XX.XXX.XXX.XX
Sender :
Recipients: <ХХХХ@ХХХХХХ.ru>
Destination IP Address:
Destination Host Name:
Message ID: 78a2_0a81_4f4dce22_a865_416f_bb58_01ba78ca0f68
McAfee Email Gateway Appliance: 01MEG02.gz.local
McAfee Email Gateway Appliance IP Address: XX.X.XX.XX .Х.ХХХ
Protocol: smtp
UTC Time: 2016-04-06_08:26:43_GMT_(+0000)
Local Time: 2016-04-06_11:26:43_FET_(+0300)

Tell me in this message is there any information about why this mail filter Mail URL Filter blocked our letter (which he did not like)?
ps: I deliberately retouched the ip-addresses of Khsami.

Answer 1

What is Mail URL Filter ?