design question: posting picture via email to our site

Question

I have a site which allows people to post pictures. I would like to allow people to send an email with an attachment to a specific email address to post the picture to our site and have it associated with the account of the sender.

Any ideas on a secure way to do this without asking the user to add a special key to their email - as this is cumbersome? The concern is that the sender email address can be spoofed.

Answer 1

Why don't you generate a very-difficult-to-guess email address for each user? I think Flickr does something like that: Upload by email.