I am using MS 365. I setup a alias Mailbox named [email protected] (xxxxx is my company name). And added it to the Delegated Accounts in EM Client for Windows (latest version).
I had to search for it, as it didn’t show up directly but I think that’s okay.
When I start em client, it wants to authenticate at MicroSoft, and it MS asked if I’m trying to setup for EM client, but when I say okay, it doesn’t do anything. Never goes to MicroSoft any further.