On drupal.org we have much less spammers than other websites. One reason is the fact that we do not allow anonymous users to post anything and that every user needs a valid mail address in order to use his account.

This poses the question: Which email providers to our spammers use?

Luckily, this is rather easy to answer:

mysql> select substring_index(substring_index(init, '@', -1), '.', 1) as provider, count(substring_index(substring_index(init, '@', -1), '.', 1)) as count from users where status = 0 and login != 0 group by provider order by count;

This results in the following top ten:

1. Gmail: 3314¹
2. Yahoo: 896¹
3. Hotmail: 475
4. Spam.la: 199
5. Nospamfor.us: 160
6. Mytempemail: 72
7. Yandex.ru: 52
8. Mailinator.com: 47
9. Mail.com: 41¹
10. Suche-project.eu: 39

All domains in this list from 4th rank on are banned from creating any more accounts.

Correction: Yandex.ru and mail.* are not blocked.

¹ Includes relevant subdomains, international domains, and aliases.