This message is specifically targeted to subscribers who use Yahoo (both the free email address service or the business email service).
For quite a while now Yahoo has been temporarily rejecting connections from my mail servers 'due to user complaints'.
I joined their Abuse Feedback Loop program so I would be informed of these user complaints.
Unfortunately, the feedback loop isn't working that well ... as my server's connections are still being deferred, but I'm not getting a lot of complaint feedback. Yahoo hasn't returned any of my emails regarding it.
You can read more about the issue on my blog: http://www.geekyramblings.org/2009/08/25/yahoo-complaint-feedback-loop-redux/
As it is now, mail sent to Yahoo hosted email accounts will probably be rather significantly delayed (at least hours).
I don't seem to have any similar problems with Gmail or Hotmail.
If you have any further questions about this, feel free to contact me directly.
Sadly, Yahoo users might not get this message for a bit of time.