Who I have the same questioned this topic

Email account I have used for 12+ to send weather alerts email to SMS (Vtext) is now failing with a specific failure return email.  I can use other emails accounts and they come through just fine.

Partial error:

Diagnostic information for administrators:

Generating server: DM8P221MB0326.NAMP221.PROD.OUTLOOK.COM
Receiving server: DM8P221MB0326.NAMP221.PROD.OUTLOOK.COM
Total retry attempts: 14

[email address removed per the Verizon Terms of Service]
8/19/2022 1:50:29 AM - Server at DM8P221MB0326.NAMP221.PROD.OUTLOOK.COM returned '550 5.4.300 Message expired -> 421 4.4.2 Connection dropped due to SocketError'
8/19/2022 1:32:12 AM - Server at vrz-sms.mx.a.cloudfilter.net (34.199.121.51) returned '421 4.4.2 Connection dropped due to SocketError'