We recently migrated to a new ISP and had to change our external IP addresses accordingly. Everything went smooth with Exchange and we were sending and receiving emails no problem.
However we've found now that our open relay receive connector is no longer working, every service that uses it (mainly logging apps and Taleo) receives a "550 5.7.1 Client does not have permissions to send as this sender" error when it tries to relay. I've triple checked the receive connector setup and even tried to create a new one following the Microsoft Tech article with no success.
Any help or pointers would be appreciated!