Issue with CCs getting emails onComment and Replies

Version of RT 3.6–
I am having an issue with users reporting that sometimes (appears
randomly) the CCs (individual emails added at the time of
reply/comment) are not getting the emails. The people that are not
getting the emails are either users with access to RT or just random
email addresses. I have confirmed that the users that have access to
RT do get CCs when they are included on the Reply or Comment. I am
however not able to confirm the random email address requests that
appear to also have the issue. If I try to reply to the ticket (not
the owner) it appears to work.

Suggestions?

I checked the Scrips for onComment and onCorrespondence. Both state
that it will notify the CCs.

I also checked the templates, they are the standard ones that came
with the RT 3.6 release.

Recommendations other troubleshooting approaches to the issue?

Thanks in Advance,

-Mark Grob