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 commentMohammad Sarosh commented
You can use Email Address Policies to change the domain of the group's email address. https://support.office.com/en-us/article/Multi-domain-support-for-Office-365-groups-Admin-help-7cf5655d-e523-4bc3-a93b-3ccebf44a01a?ui=en-US&rs=en-US&ad=US