OK, just IMMEDIATELY got this after trying to send a TEST message and I DO RECALL my Webbie addy :-):

"postmaster@outlook.com
​
You
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DS3PEPF0000C37C.mail.protection.outlook.com rejected your message to the following email addresses:

sxxxxxx@webtv.net (sxxxxxx@webtv.net)
A communication failure occurred during the delivery of this message. Please try to resend the message later. If the problem continues, contact your email admin.


DS3PEPF0000C37C.mail.protection.outlook.com gave this error:
Requested action not taken: mailbox unavailable (S2017062302). [DS3PEPF0000C37C.namprd04.prod.outlook.com 2025-06-08T18:24:57.798Z 08DDA5E7AE396620]"