[nickrj]

SMTP is the protocol that mail servers use to send messages between each other, both sending and receiving. POP3/IMAP are protocols that your email client will use between itself and the mail server which allow you to view messages.

edit: I should note that you're correct in that SMTP is used by the client to relay email messages to the server also.

[pan69]

Thanks for that. So what exactly would you be able to use this for?

[tdfx]

For one example, this would certainly take care of a lot of the work necessary for creating a disposable email service.

[FuzzyDunlop]

One existing use-case is Facebook's 'reply to this email to post a comment' feature.

[sprobertson]

Looks like it could be used in an application that needs to send email without relying on a platform-specific SMTP server or external service.

edit: I'm wrong, listen to this guy ->

[kenneth_reitz]

It's actually for an application that needs to receive an email.