Devletters started as a tool to enable Group Admins reach out to their members, and pass information easier. A user can chat with Toby, the Devletters bot on Facebook Messenger to select the dev communities around them they are interested in. They can get more information about each community, and have the option to subscribe to updates from specific communities.
For each community they subscribe to, the Admin or Lead of that community, from their dashboard, can send messages and update members of the community about latest information, upcoming meet ups, tips, etc. The members would receive messages on Facebook Messenger.
There are also specific links with a referral like m.me/devletters?ref=forlooprwanda that community leads can share with their members to ask them to subscribe to their community.