The aftermath of being spammed part 2

If your moodle site allows email based self registration (is enabled) and then you turn it off (not enabled)

Site admin | plugins | authentication | manage authentication

This setting

The accounts that were created this way will not longer work!  This is from the email self register moodle doc,
"Note: The Email-based self-registration authentication plugin must be enabled to allow users who previously self-registered to login. Selecting Email-based self-registration as the self registration method allows potential users to self register. "

The way I see it you can either:

leave the email based self registration enabled and add a reCAPTCHA key and/or specify a domain to limit where new accounts can be created from.

or

you will have to somehow figure out how to *reactivate the accounts effected (those created with the previously allowed email based self registration plugin.  Perhaps a bit field in an associated record in the DB that specifies what the authentication method was?  Something like if the value is 2 for all the records created with the email based self registration plugin, change them to 1, which is the value of the manual authentication plugin?  I am only guessing here, did not check this.