That seems a bit heavy-handed! Can it be turned off? It would seem you're not even accepting them. I'm getting messages like this from my mail server. Code: After 3 hours, the following addresses had delivery problems: firstname.lastname@example.org [Temporary failure - still trying to deliver] If they ever get delivered, you're going to get a bunch of them because I have been plugin-programming today (and not having a good time of it!). Or perhaps I have been blocked for sending too many error reports.