An additional feature of the MailGun module is email validation.
When the module is properly configured it will use the Mailgun API to validate your users' email addresses at a rate of 100 per hour.
Why is this necessary?
If your were to send a newsletter (for example) to all of your (1000's of) users, and many of them were old users whose email addresses were no longer valid, those emails would 'bounce' and the Mailgun systems would then suspect that you are a spamming site and block you.
So it is necessary to ensure all user email addresses are validated prior to using them. When the MailGUn module detects an invalid address it will be tagged and Jamroom will not send any email to that address any longer.
This is especially important
when user accounts have been imported to Jamroom 'en masse' (for example from a Ning archive). In that situation it is very important that the MailGun module is implemented and given time to validate all imported emails prior to the site going live.