Suggest getting your company to check that the reply-to email address they are using on their email is valid. More and more email companies (Google for example) check the reply-to email address on incoming emails (especially broadcasts) for validity before accepting the mail. If it is invalid, they just don't accept it - the sender doesn't get a bounce notice because their email address was no good, you don't get spam or junk because the email was never accepted.
This is a spam/malware prevention tactic, and it is actually quite effective.
Also Google caches bad email addresses to save time in checking, so even if the bad return address is reactivated it may take a couple days before it clears.
Jock