Well my point wasn’t that doing this would fix your hotmail problem - just that if hotmail were rejecting the messages, you’d be receiving the bounces (you would be receiving them if the envelope-sender were firstname.lastname@example.org too - it would be going to the mailbox for that user - it’s mostly in the case of mod_php where it’s especially important to set this, since in that case, it’s the Apache user that’s sending the message).
So anyway, my point is that you should make sure that the messages aren’t getting rejected by hotmail.
If the messages aren’t being rejected and aren’t showing up in the junk mail folder, there’s not a whole lot that we can do. It’s generally a bad idea (in my opinion) to just silently drop mail, but some sites seem to do it.
Just out of curiosity, if you do:
echo ‘blah’ | mail -s ‘test’ [address]@hotmail.com
(replacing [address] with the person’s hotmail address, of course) they you receive the message?
If you don’t already have one, you may want to setup a test hotmail account for the purposes of testing.
If you submit a support request with an example of a hotmail user that’s not receiving the message, I can take a look in the logs, but I’m pretty sure they’re not explicitly rejecting mail from our machines.
It should be a valid address you check, but don’t mind getting lots of bounces to.
Note that in this case of any sort of bulk mail, we require that you set a valid return-path and remove any addresses which bounce permanently more than a few times.