There are plugins to allow easy user switching, and I think that would be your safest bet. This way they can just create users in the admin area with new email addresses, and switch to being that user without logging in or out.
Because WordPress uses email addresses for verification and authentication purposes, it can’t really have the same email address multiple times safely.
Thanks John – user switching type plugins is one option I am looking into now.
I was thinking if once I register the users using a ‘1@myemail.com’ type email address I could simply manually edit the email address within that users area but no idea if that will unleash a lot of issues somewhere down the line?
As of WPMU 2.8.1 this will work, but with 2.7.1 if you changed an email address, it didn’t get changed in wp_signups, so even if you changed the email address, you still could not reuse the original one you used to sign up. Be careful right now using 2.8.1 as there are several ways that it’s not playing friendly with BuddyPress.
A user-switching plugin is probably the easiest and safest bet, in my opinion.
Thanks again John.
Is manually hacking the SQL database a no no to try and get around this wp_signups ‘issue’ then? 
I will look into the user switching plugins first thing in the morning here in the UK.
I also steering well clear of 2.8.1 as the main site I am working on is only just launched and we need something that is at least generally considered stable!
Using 2.7.1, manually digging into phpMyAdmin and editing the wp_signups table is the only way around it. Not going to lie, I’ve had to do it once or twice myself. 
One thing that may help in the meantime is using gmail.
for example, I have account ‘myaccount@gmail.com’
you can use others that will all resolve to that account such as
‘username1.myaccount@gmail.com’
‘username2.myaccount@gmail.com’
‘username3.myaccount@gmail.com’
gmail will route all the ‘sub’ accounts to the same email account for you. For me at least it makes it really easy for me to manage all of my accounts, and it’s really simple to remember as I use ‘username1’ as the username1 for my wp account in question….
Many e-mail services also support “plus addressing” – including gmail. I usually use “myname+mysitename1@gmail.com”, “myname+mysitename2@gmail.com”, etc. See http://en.wikipedia.org/wiki/Plus_addressing#Sub-addressing .
I have just come across sub-addressing myself yeah – looks like the perfect temporary fix
My own domains email accounts don’t allow it easily but I will just create 1 gmail account per user that needs multiple accounts.
Thanks for your help guys.
