I viewed Should multiple user accounts be allowed to use the same email address?

My problem is that we're writing the new version of our website, but need to migrate the old user database to the new system. In the new system, we want users to be able to use emails as their unique username. Currently they use an autogenerated member ID as the username, which is hard to remember.

How can we get around this problem? Is this a problem commonly faced?

  • Why do your users have multiple accounts?
    – Ren
    Commented Oct 22, 2019 at 12:43
  • 1
    Would merging accounts that belong to the same email make sense for your website?
    – DasBeasto
    Commented Oct 22, 2019 at 12:44
  • @Ren I think historically, there's been a good chunk of the userbase that were old people sharing an email address, but it seems now that around 85% of our user base has a unique email, and a lot of the remaining users are businesses. Commented Oct 23, 2019 at 6:35
  • @DasBeasto the accounts can belong to multiple different people, which is the main reason that we can't just merge them. The accounts might also belong to different public institutions that make orders using the same mail - for example a municipality ordering our products for its institutions, if that makes sense? Commented Oct 23, 2019 at 6:37

2 Answers 2


Very interesting problem.

Combine accounts

Combine the accounts but have multiple users within an account. Something like Netflix where you can choose your user after logging in. Force users to create a name for their user so they can distinguish themselves.

Additionaly you could make an annoying banner that keeps popping up after they login that tells them they should have unique email addresses. That might get a few users to update.

Force new email

Basically what you're suggesting is every user needs their own email address. You could for force them to change their email address after logging in. To make it a bit nicer you can add some help text and links to popular email providers. But likely this will be something for them to discuss with their IT department. I think this will suck whichever way you make it..

  • Force new email is the way to go, imo.
    – Adriano
    Commented Oct 24, 2019 at 23:07

I think your biggest obstacle is that you want to treat email addresses as unique, but they are not.

What you could do is allow users to login via email or user id. If they enter an email address that is tied to multiple accounts, demand that they select their user id from a dropdown account. Display:

Your email address is used by multiple accounts. Please additionally provide your user id or log in with your user id next time.

Did you know that you can migrate your data over to new accounts with unique email addresses? Click here.

Of course, you should then go and implement a way for users to migrate their single-email-multi-account setup over to accounts with unique email addresses.

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