How to use same email for multiple users

I have a very big multisite. And I got a request to enable option that multiple users can use the same email. I found a plugin “Allow Multiple Accounts” which doesn’t work properly. I should figure out some other solution for that. I know that I could use something like adding +sometext to every email, so it will show different to WordPress. Do you have some other solution, that can be done here?

Getting a List of Currently Available Roles on a WordPress Site?

When writing WordPress plugins there is often a need to set up options for which roles on the site have access to certain functionality or content. To do this a plugin dev needs to fetch the list of roles that exist on the site to use in the option. Because custom roles can be created we cannot assume the default roles are the only ones available.