Emails not being sent - I see them in sent folder but recipients are not getting them

When I send an email from my [Edited: "Personal Information"] account, I get the acknowledgement that mail is sent and i see the sent mail in sent folder. But the mail is not being delivered to the targeted recipients.

I have tried this from Outlook on my PC and phone as well Xfinity website (connect.xfinity.com).

I have had this account for 15 plus years and didn't have this problem until a few days agi.