Return receipts are getting stuck transferring in the router

Return receipts to internet are getting stuck in the router. The router task shows on the Admin Console like this:

[0000000A] Transferring next message (Notes n:nnnnnnnnn) to db.com(host smtp2.db.com.

The message never goes out. The router can not be restarted with a a domino shutdown/restart. This may or may not have started since our upgrade from 6.5.6 to 8.0.2.

Any info is appreciated!