Thanks for the feedback @aleksjablo!
Mattermail was created by a community member with the intention to listen to an email box and publish all received emails in a channel or private group in Mattermost.
If you would like to see a more complete email integration such as the one you referenced, I encourage you to upvote an existing feature request for email integration. Each member receives 10 upvotes in uservoice, influencing the future direction of Mattermost.