Just got this upon posting:
SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: Mail rejected by the processing module: 5.1.1 xFAFbnQVJi1Z4 Recipient Undeliverable (TT512) SMTP code: 552
Weird, I sure didn't try to send any data (other than the post) or mail. The post got published, though.