Outlook.com emails being rejected and returned by sbcglobal.net, att.net

I am aware of other questions being posted regarding this issue, but most seem to directed to corporate email, and not individual home users as myself.

As best as I can tell this problem started yesterday, August 6, 2024, when any email I sent to an sbcglobal.net or att.net email recipient was rejected and returned with the following message:

Undeliverable: Fw: PRAYER BREAKFAST, SAT AUG 10, 2024, 8 AM, at MIMI's CAFE

To:​ You ​ Wed 8/7/2024 5:15 PM

This message is able to be sent again Send again

Delivery has failed to these recipients or groups:

<recipient email address>

Your message wasn't delivered. Despite repeated attempts to deliver your message, the recipient's email system refused to accept a connection from your email system. Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their email system is refusing connections from your email server. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

The remaining information contained in the bounce message applied to email administrators, which is not applicable to me as a home user.

This problem occurs on both my windows 11 laptop, and my iPhone 13, and occurs with both classic Outlook and new Outlook. It occurs rather I send to a single recipient to multiple recipients in my contacts list.

I was able to send emails to these recipients as late as last Friday, August 2, 2024.

What solutions does Microsoft have to help resolve this issue?

This

Thank you,