P365: Delayed ERS mail delivery when using Proofpoint during domain cutover (4298041)

Issue

Customers using Proofpoint servers as their ingress point for all Internet Mail may observe ERS mail delivery delays during domain cutover. This is because by going through Proofpoint, all inbound mail to the Power365 mail relays will originate from a single IP address causing rate controls to applied. 

Solution 

Prior to domain cutover, customers using a 3rd party email provider or relay to direct mail traffic to the Power365 ERS mail relays should attempt to bypass the border relays if possible to avoid delays. 

If that is not possible, please contact Quest Support prior to domain cutover to investigate having these systems whitelisted for rate control to mitigate potential delays.