Deprecation of Mail flow features in classic Exchange admin center in WW service

Peter_Holdridge my apologies I gave Erica the wrong information, confusing it with a transient issue I ran into last week whereby you couldn't 'resolve' or search on addresses that weren't in the directory (e.g. an external address). That issue was indeed transient. You are right in the new EAC you can't search by proxy address whereas in the legacy EAC message trace you can. You can also do it in the Message Trace in the legacy Security and Compliance Center (you enter the proxy address, e.g. kev@lunadream.com, then press enter). 

While this works in the SCC Message Trace, indeed this doesn't work in the new EAC Message Trace, where you're forced to enter the suggested primary SMTP address exactly as you described. We've opened a work item to fix this ASAP.

Again, my humble apologies for the initial confusion. Please let me know if I've still misunderstood your report.

Best wishes,

Kevin Shaughnessy
Sr. Program Manager
Exchange Online Transport