Hi, @Tom1156
You have already deleted your e-mail address, but please double-check if there is a linked e-mail address.
You can use the following command to view the results. If the address exists, you'll see the relevant recipient information. If the address does not exist, no results will be returned.
Get-Recipient -Filter "EmailAddresses -eq 'smtp: pgreen@somethinggroup.com ' "
You can also try adding the email address as an alias for a shared mailbox. Specifically, after you create a shared mailbox, add pgreen@somethinggroup.com as an alias, then set it as your primary address and delete the old address.
It should be noted that the time for the configuration modification to take effect is affected by the configuration of the system or organization, and the specific time may be slightly extended.
Same problem as you here exchange - SMTP Address re-use in Office 365 - Server Fault
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