I wouldn't recommend doing it on your own, or at least use a well known smtp server for relay (where you have access to). Especially hotmail can be very tricky

I wouldn't recommend doing it on your own, or at least use a well known smtp server for relay (where you have access to). Especially hotmail can be very tricky. If a few users complain about your mails, they will put you on a ban list and your emails will be routed to /dev/null. Tehy won't even appear in the spam folder of the user.