The official MEI mailing list, MEI-L, is used to inform the community about upcoming events, discuss possible improvements for MEI, evaluate encoding strategies and models, and get support from the full community.
The list is open to anyone for subscription, and everyone is welcome to join MEI-L by subscribing to: https://lists.uni-paderborn.de/mailman/listinfo/mei-l.
Also, the archives of the list are open to the public and can be browsed online: https://lists.uni-paderborn.de/pipermail/mei-l/.
Normally, there is not much traffic on the list, but the tone is friendly and most questions are answered within the first 24 hours. So if you have a particular question about MEI, please let others learn from your responses as well by asking there in public.