There are some limits on mailcatch SMTP server to disallow too many connections from the same hosts at the same time, but it should not affect things like yahoo/...
The server was a bit overwhelmed for a while but recently (like a few hours ago ;) I have set up a new code update that should make it handle things much better. Time will tell :)
True enough.. i'm doing it this way currently because I can simply count the number of connections per IP and clsoe them as soon as they come if over the limit. If I check the target it will be further in the request.
But yes this could be done. I had planned to do some improvments to the SMTP code soonish, I'll take a look