provided by Star2Billing S.L.

Yes callingcard, you could do that and in theory it wll work. But on the other hand, it will be an uncontrolled error and the database will throw an error if someone trying to create a duplicate email.

I suggest that you handle it after the form has be submitted. Usually, here is what people do: they collect the data received for the form, and before putting them in the database, they grab the email and make a query to the db to see if that email is already there. If it is, they will display the appropriate message to the user. Sometimes, if you don't want to let them know that the email is the issue, then you can simply abort the signup quietly, but you still must update the logfiles so administrators will know what's going on. Because if the users know that duplicate emails are not allowed, they will simply use some alternatives like http://trashmail.net

Ok, I will add it to my todo list cause I might need it too.

But some times, I also need to allow duplicate emails. The administrator, for example, may need to have to create several account for testing purposes. Or sometimes, on client maybe taking take of many accounts, his own, his kids' and wife's and so on. So he would like to receive the email cause he is the one paying for the accounts. I think that a quick fix can be done for your case. And a permanent fix will look like this:

- In the global configuration of a2billing, add an option to allow or disallow the duplication of emails
- In the signup section of the config, add an option to allow or disallow the duplication of emails for the signup only
- In the customer form, add a field that will authorize duplicating his email. Only the Admin will have access to it.

Maybe some of those options don't make any sense. I am open to suggestions.