Just when I was getting excited by you saying that only a few emails were bouncing.... Hotmail is a nightmare to get right, as they keep changing their 'requirements' for a well behaved mail server from which they will deign to accept mail. Whatever their corporate objectives, the free exchange of email is very low on the list.
Just about every forum I visit has a current 'HOT' topic along the lines of 'Problems sending mail to Hotmail', 'Hotmail mail stopped working' etc etc.
I would suggest setting 'Send from known domain to true or yes, and use sendmail -f as well. That may help. You should also check that your mail server/your hosting co's mail server is not blacklisted. If you are sending from a home broadband line, you are almost certainly blacklisted by default. You also need an SPF record in your DNS, and probably need to register with the Hotmail SenderID programme.
Oh, and get all the headers, encoding and charsets etc correct in your emails, or all the above is in vain.
Next week, who knows.



