Cafesolo wonders: "I'm developing a web application using PHP. It has a user registration system that sends a link via email to activate new accounts. I've found that sending mails to Hotmail accounts is very difficult, because the spam filter is very strong and it filters lots of non-junk messages. I think the spam filter blocks any email whose domain isn't in an internal whitelist (which might contain popular domains, like hotmail.com itself, gmail.com, yahoo.com, msn.com, etc). Most of my users have Hotmail emails. I can't simply tell my users to read the junk folder because most of them are not computer-savvy and that seems to be a bit confusing to them. Has anyone managed to solve this problem? Did somebody try to contact Microsoft? Is there any way to get whitelisted? Can an independent programmer get his domain whitelisted?"
Computers are unreliable, but humans are even more unreliable.
Any system which depends on human reliability is unreliable.