It could be server problems at the ‘recipient’ end. I doubt either would be scanning and rejecting based on content.
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Years ago (about 10 or so) I sent an email to Glen Beck via his website at the time. Some how, a virus apparently entered the process. I still occasionally get ‘bounce’ notices that the email is undeliverable. The reject shows several names that I have never had any connection to. I think it was a ‘collector’ email virus that captured @addresses.
I’ve had problems with Beck’s web site. I don’t know if he knows but his website is regularly under attack.