preserving link from email through login to post

[eluser]new_igniter[/eluser]
can you point me in the right direction?

I am looking to generate an email with a link to a post on my site, that requires a login, but allows the user to continue on to the post, after logging in.

So basically, someone gets an email, they click on the link, they log in, they then go to the link (some post id) in the email.