I think this is fundamental to WordPress as you can login or recover password with either username or email.
I had the same problem with some members of a croquet club. I was able to convince them that sharing an email account was a very bad idea as so many online systems take your email address as your identity.
Allowing duplicate emails is nearly impossible to do in a robust manner. WP’s schema requires 2 unique elements for a user – a unique user_login (username) and a unique user_email. It’s fundamental to WP’s structure.
There are ways to circumvent that, but I HIGHLY advise that you not go down that road. You’ll run into a lot of other unintended problems because WP has specific functions when creating and updating users that have to be circumvented. In some instances, such as the admin-side user profile update, you simply cannot circumvent that process. You end up running into a lot of unintended problems – and then when you think you have it working, something else will come up.
This is fundamental to WordPress, not WP-Members, so even if you find some other plugin that does it, you’re circumventing something that is a core part of WordPress (read: NOT something that should be changed).
[oops, Chad, answers crossed, I apologize, post updated]
@smfisher Thanks for your answer.
I have the feeling you unfortunately may be right, but am seeking confirmation.
If confirmed, it is going sadly going to be a blocking issue for us, I’m afraid, and I’ll have to look into another solution that does not equate “club member” and “WP user”.
– – update
@chad, thanks for your very prompt answer.
I completely understand and I agree we shouldn’t try to abuse such a core WP structure. I think I will have to handle memberships outside WP, then.
Unless I can find a club management plugin that does not handle “club membership” within the WP account management features.
Case closed, impossible/undesireable.
Thank you for the plugin and the support.