Facebook's m.me service that shortens the URL that redirects clients to a person, page, or bot in Messenger can be used for web sites, email newsletters, and much more.

When a client starts a new conversation or continues an existing conversation with your bot through an m.me link, the following message can appear in the conversation: "You accessed this conversation via a link. We'll let NAME_OF_THE_PAGE know you are here."

The format for the link is http://m.me/PAGE_NAME, where PAGE_NAME is the username of the Facebook page that the bot is linking to.

In the example below, an email is sent with the m.me link and you can access the conversation directly from a mobile phone or desktop.

You can access more information in this article from Meta.