Associate Existing Email Address with An O365 Group

In attempt to connect a classic site (https://contoso.sharepoint.com/sites/abc) to a new Office 365 group, can an existing email address, such as abc@contoso.com, be associated with an O365 group (same name)?  If so, how do we go about associating them so the username, 'abc', matches the group name and the site name?  That way, we don't have to create a different group email address, that is different from the site name.  It be nice to be consistent.

The screenshot below shows that the group email address is not available since it already exists but would like to use that existing email address to be consistent with the site name and group name.

Any guidance would greatly be appreciated.