gitlab-org--gitlab-foss/doc/user/admin_area/settings/sign_up_restrictions.md

Sign-up restrictions

Blacklist email domains

Introduced in GitLab 8.10.

With this feature enabled, you can block email addresses of a specific domain from creating an account on your GitLab server. This is particularly useful to prevent spam. Disposable email addresses are usually used by malicious users to create dummy accounts and spam issues.

This feature can be activated via the Application Settings in the Admin area, and you have the option of entering the list manually, or uploading a file with the list.

The blacklist accepts wildcards, so you can use *.test.com to block every test.com subdomain, or *.io to block all domains ending in .io. Domains should be separated by a whitespace, semicolon, comma, or a new line.