The preferred method of contact with the MRBS development team is the main MRBS mailing list, email@example.com. You can send absolutely anything there - you can sign up or browse the archives from the mailing list management page. Note: You will not be able to post to the list until you subscribe, but you can subscribe and disable email delivery (or choose to receive digests) if you prefer. This is a measure to keep the mailing list free of spam.
If you prefer, you can use the bug/support request/feature request trackers available on the project page:
Please do not contact the MRBS developers or administrators directly - we generally only work on MRBS in our spare time, and prefer not to receive personal email from users directly. Emailing one person directly rather than using the mailing list or trackers will also reduce your chance of getting a useful reply in a timely fashion.