Multiple @comcast.net emailers receive mailer-daemon because their email is not delivered to one specific address

Something has changed recently at the @comcast.net servers!  My wife has an @comcast.net email acct, and her emails to my personal email (@xxx.org I'm anonymizing it) never go through.  Then I polled other contacts with @comcast.net emails, and asked them to send me a test email.  All of them failed.  The destination email server is working fine, and I can receive emails there from everyone else. So something is wrong with comcast.net.