After replying to one of my client’s emails, I received this error message from the mail server:
The message carried your return address, so it was either a genuine mail from you, or a sender address was faked and your e-mail address abused by third party, in which case we apologize for undesired notification.
We do try to minimize backscatter for more prominent cases of UBE and for infected mail, but for less obvious cases of UBE some balance between losing genuine mail and sending undesired backscatter is sought, and there can be some collateral damage on both sides.
Delivery of the email was stopped!
It looks like English, but I have no idea what it means. What is backscatter? What am supposed to do? Oh, and that exclamation point is theirs, not mine.