Summary
In Mastodon we can set LOCAL_DOMAIN for the domain part of ActivityPub users and WEB_DOMAIN for the web access part of it.
This way we can use any domain for access mastodon but the users still match the main domain (like email, for example).
We can have an user@example.com email, but access it from webmail.example.com.
As we can see in https://docs.joinmastodon.org/admin/config/ there are an option for it.
And this doc explain how to do it https://github.com/felx/mastodon-documentation/blob/master/Running-Mastodon/Serving_a_different_domain.md
Summary
In Mastodon we can set LOCAL_DOMAIN for the domain part of ActivityPub users and WEB_DOMAIN for the web access part of it.
This way we can use any domain for access mastodon but the users still match the main domain (like email, for example).
We can have an user@example.com email, but access it from webmail.example.com.
As we can see in https://docs.joinmastodon.org/admin/config/ there are an option for it.
And this doc explain how to do it https://github.com/felx/mastodon-documentation/blob/master/Running-Mastodon/Serving_a_different_domain.md