You can now use a dot in the email alias. We are working on providing the ability to edit the email address of a group after creation.
For the ability to edit the email addresses, we now have the following roadmap item: https://products.office.com/en-US/business/office-365-roadmap?filters=&freeformsearch=27891&featureid=27891
An error occurred while saving the commentClaudio Torres commented
at bare minimum the email alias today should use the prefix/suffix added to the naming policy of dist lists in exchange admin. As of now the naming only applies to the group name whereas the email sticks to name without the added policy. This makes it possible to any user to create whatever group they want and "lock" the email adress within our total domain scope. I would really want to separate the group default email naming scheme from our manually created /admin/ groups/user emails.