An email bridge is something that allows messages from Elgg, group discussion messages, direct message notifications etc, to be directly replied to from your email client.
I needed to get something like this implemented for a client project, and thankfully there was a third party open source plugin written by Michael Jett which did most of the work for me.
The Jettmail project is still under active development, and at time of writing was missing two key bits of functionality that I needed:
- Direct reply-to email functionality (you could send messages from an email link, but direct reply-to functionality was missing).
- Direct person to person message support.
I have made my own modifications to Jettmail to add this functionality, and also created a plugin to rewrite the reply-to email line appropriately for each object.