This "sharing email address" topic is a big problem also in my communities as it means we can't have a complete member registration based on Community Builder.
Nant description of an easy solution to the problem looks so fine - but unfortunately I can't get it to work for all addresses. Can it be so,that it is only XXX@hotmail.com, XXX@gmail.com who support +tag qualifier?
My page is fully updated to Joomla 2.5.14 and CB 1.9

this solution is stupid. People (church, which Couples dating, 18 + adult sites) simply do not want this, they want one email address. They want one username. But they want two (or more) people to view.

one account for more people. So what should actually be an extension at least 2 fields for gender, date of birth, height, weight, you name it .... That would be a communty builder really should be.

Let that the participation are to the core of Joomla.

Nick, thanks for this information. I tried successfully with a gmail account. However, our problem is we have several hundred members (older folks) who don't have email addresses so our only means of communicating with them is via snail mail. This means we have to generate a mailout for printing. We have given them all a dummy email address to get past the Joomla barrier and thanks to your advice I've amended this address to 'ouradmin+tag@ourmail.com' where 'ouradmin@ourmail.com' is our administration inbox. The idea is to be able to use the Mailer to generate 'letters' to these folks based on selecting the tagged addresses and collect the resulting emails from our admin inbox from where they can be printed out for insertion in envelopes and posting. Will this work or have I misunderstood?