All other ISPs (Google, AOL, Hotmail) are fantastic, hitting 98-100% in the inbox. Yahoo is very random, and lately our deliverability has dropped drastically. All IPs are senders certified by Return Path and supposedly that automatically whitelists our IPs and allows us to send as many emails as we want (from what my boss says). Do I bother with applying to Yahoo's bulk sender form? I run every email campaign through: SpamAssassin (Excellent Scores) Test Accounts (for test deliverability) Old school HTML format I'm running out of ideas and I'm starting to be in the hot seat and I am very fearful for my job position. If you can offer any wise words i will be very grateful. Thank you in advance.