Best to start with telling us what kind of hosting plan, control panel, etc. you have, as well as your willingness to use an outside service or change your hosting plan, so we have some idea what kind of solutions might be possible. As well as expected volume and usage, etc.
Do keep in mind the non-technical implications. One spammer can bring you major trouble.
Offering email to your users is not something to be taken lightly.
I agree- the more and more I look into this the more I am seeing that it is quite a lot more involving than I initially expected.
I will be hosting the site itself at Dreamhost most likely. I basically want the person to be able to have the option to create an email address when they join the community style site that I am creating.
I was actually thinking about doing something similar over the weekend, but two things scared me off:
- Spammers, who could sully my good (domain) name - Abhorrence of providing tech support. When DreamHost has (another) surprise down-time, do you really want to field your member's questions about when their email will work again? And if there's a server problem and you lose their email, people will be very angry. (I don't use dreamhost for my hosting anymore, but even with my new host I foresee too great a risk of problems.)
Bottom line: I probably won't do it. Except maybe for hard core members and friends.