Hotmail is typically deleting all emails that I am sending, and especially
registration keys which it is deleting, and killing, and destroying,
and it's laughing when doing it.
Lost Registration Keys
If you've buyed a registration key from a paypal account with hotmail address, there's no chance that you will ever receive it, send thanks and flowers to hotmail support. For the reg key, please let me know of an alternate email address (non-hotmail) where I can reach you, and please also include your original hotmail address, and the paypal transaction ID (or other proof that it's been you whom was sending the money, like a description of the envelope that you've sent per mail, and the date when you were sending it).
As far as I understand, the so-called hotmail spam filter seems to passing only messages from commercial mainstream software (eg. outlook or netscape). But none from less popular programs like no$msg, not to mention from registration key generators.
Identifying mainstream software probably works like so: For example, with netscape 3.04 gold, the 16bit component of the Message-ID seems to be just random, but the 32bit component contains the time, in seconds, since 01 Jan 1970 00:00:00 +0000, including leap years, excluding leap seconds, which must be in sync (plus/minus one second) with the message Date line.
Using a faked message header of that style might break the hotmail spam filter, anyways that's definetly NOT how mail delivery should work. And, most likely, hotmail would soon find another way to fuck you up.
So, the best way to break hotmail is: Don't use it.