I've been playing with the eMail block as an alternative to the Messages block. Have found it very stable and it offers a quick and easy way to send a message (with an attachment) to specific users. Of course, if you want to communicate to everyone in a group you would use the Forum module. The only drawback is that, unlike the Messages and Forum in Moodle, the eMail block only sends an alert to the recipients email address NOT the post itself.

This block would get a higher rating if the actual post was emailed to the recipient.

Overall Rating: (3.5 stars)

Link to Read More or Download: eMail block on moodle.org