This is probably one of the tougher things new techs have to figure out.
ARS
One place you can start is here:
Mitel ARS Programming for Security. It may help some on how to figure out your COR.
But let's start with what is COR? (Class of Restriction)
COR is an assigned grouping of devices or trunks for the purposes of restricting trunk usage.
If you look at the Class of Restriction form you will see that it's a massive table.
The COR numbers on the far left column are the COR numbers assigned to devices and trunks.
The COR numbers across the top are the COR Classes the COR Classes on the left are restricted from using.
To try and give an example of that:
If on row 4 you see an "R" in column 2, then any device with a COR of 4 will not be able to use a route that has a COR of 2 assigned.
COR does not restrict device to device, only device to a route.
Now let's use this as an example (This does not apply to your site - it's a generic example):
You have a user with a COR of 10.
If you look in the COR table and look at 10 on the far left column you will see that 10 is restricted from 1,2,3,5,6,7
Now look at your routes.
Route 21 has a COR assigned of 3.
If the user dials an ARS digit string that hits Route 21 the call will fail because COR 10 is restricted from any route with a 3.
Route 22 has a COR assigned of 4.
If the user dials an ARS digit string that hits route 22 the call will be allowed because 10 is not restricted from 4.
I hope that helps.
Odds are pretty good that your SIP route for international calling does not use a COR that is restricted from anything.
Ralph