Hi @George Reitnour ,
Welcome to our forum.
Why, when my cellphone, through Office365, can send and receive emails via MyName@MyDomain.com
Could you connect to your account normally in the browser of your phone?
Did it display any error on your web mail and desktop client? Also, in order to further confirm if your issue is related to your account or your client, if it's possible, it's suggested to log in your account on other PC for testing.
If it could work normally on other PC, the issue may be related to your PC itself, considering it occurred on your web mail and Outlook desktop client, in order to avoid the interference of internet and firewall, it's suggested to switch to other internet and close your firewall to check.
Also, if the issue still exists, it may also be caused by any anti-virus programs, it's suggeted to close your antivirus programs temporarily and re-log in your account to test.
If the issue could actually reproduce on other pc, I'm afraid it may be related to your account itself, it's suggested to contact your admin directly to check.
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