List all users with a given email domain

[Lilly]

You should be able to do this by going to the admin - active users list at your-site/admin/users/list/active then type the email domain in the search filter

also, these topics might help you:

Troubleshooting Outgoing Email

This is an explanation guide discussing how admins can troubleshooting outgoing email from a Discourse site. Required user level: Administrator Discourse relies heavily on email for user notifications and account management tasks. If users are unable to receive emails from your Discourse site, this can lead to a variety of problems. Summary In this documentation, you will learn: How to check sent email logs Investigating skipped and bounced emails Common …

Troubleshoot email on a new Discourse install

You just installed Discourse via the install guide, but email doesn’t seem to work. Unfortunately this means you can’t log in as an admin to finalize the install. Let’s troubleshootize! Try the doctor If you run ./discourse-doctor it will check several ways that your mail configuration might be broken, and offer advice. Try that first. Did you enter email settings correctly? The simplest way is to run ./discourse-setup again. Did you enter everything correctly? You…