One of our clients received an email from us (from a Marketo campaign) with [*MARKETING*] in the subject line.
I.e. instead of "Thank you for coming!" in the subject line, it read "[*MARKETING*] Thank you for coming!"
Obviously, we never typed [*MARKETING*] into the subject lines of any of our emails.
Any idea how something like that could happen?
That text is being added by the client's anti-spam/anti-abuse server, which is using heuristics (perhaps based on the source IP) to classify the mail. And of course it is accurate, so it's hard to call it a false positive...