To avoid bulk private messaging by spammers in busy Drupal 6 community site, I'd like to limit the messages an authenticated user can send out in certain time span. I saw Private Message Limits but it is still in dev since 2011 hence it may not be ready for production. So I'm wondering what is the best way to apply the limit? Thanks
Privatemsg 6.x-2.x has a Limits submodule built in, either use that version or use try out the separate project for 6.x-1.x, you will have to find out yourself it is working well enough for you.