I find SenderBase to be much more sensitive then SenderScore. Mailing GI exclusively on separate IPs, my SenderScore is hovering in 97-99 range for most of the time. SenderBase, however, tends to become 'Good' after first few mailings, but then slides to 'Poor'. I'm trying to mail data that affects SB separately to narrow down the issue, but can't seem to weed out all of it. What are the mx servers that are connected with SenderBase besides ironport? And what's your experience with maintaining good rep with them? P.S IPs are not listed on any blacklists.