Shal's reference to gmail using "+" in some way associated with aliases, is not consistent with the observation (by me and others) that gmail truncates leftsides at a "+" . An email to username+anytext@gmail.com is delivered to username@gmail.com and NOT rejected back to the sender as "No such user". The link Shal gave to a Gmail help page about aliases doesn't contain any reference to the "+" character..
Dave's reference to moderators "using this to chat to each other" is a reference to using the <groupname+owner@groups.io> address as a mini-group.
