Known Users
Large Scale Haraka Users
Cloudron - A platform for self-hosting web apps
Craigslist - Over 20 million emails a day through Haraka
Email It In - A service to email files to Google Drive, Dropbox or Skydrive
Fort Anti-Spam
Mail.tm - Your Own Protection Mail
Mirus Research - Address simplification/forwarding services
Temp Mail - a Temporary Email Address provider
ThreatWave - Hidden insights and data from email - over 150 million emails a day