This is courtesy of Laura over at Word To the Wise, from a very good article located here: http://blog.wordtothewise.com/ Please see my comments in red and feel free to debate/discuss/topic. IP Address reputation primer - How is IP reputation measured? While each spam filtering company and ISP have their own ways of calculating the reputation of an IP address, there are some similarities in what they measure. How many non-existent email addresses is this IP attempting to deliver to? Hard bounces get removed daily over here. How many abandoned email addresses is this IP attempting to deliver to? How am I to determine an abandoned email address? What is an abandoned email? I have to assume an email that has not been logged into in 4-5 months. so the only way to effectively assume this is to purge your data of all people who have not opened or clicked in 5-6 months, right? How many "known bad" email addresses (spamtraps) is this IP attempting to deliver to? Fair enough - should be nil if it's real/legit optin data, yet we all know this isnt always the case. How many recipients complain about receiving this mail? Not many that I'm aware of, at least not to upstreams... how many complaints do you guys get per week? How many recipients complain about not receiving this mail? lol. This is a very good question. I'm wondering if we shouldnt now put a little blurb at the bottom of our emails, "If you DONT receive our newsletter each day, please complain to each of the following domain postmasters, whose addresses are listed below" How respectful of my resources is this IP? What are they expecting here, anyone? A courtesy of an email when the bandwidth graph spikes a bit saying "Sorry man" Does this IP keep connections open for long periods of time? Define LONG. I'd love to know. What do you think? Does this IP retry deliveries too aggressively? Define aggressive please - thousands of email marketers would like to know the magic number so we arent too aggressive. But be realistic, mail needs to go out fast. Does this IP stop mailing addresses after receiving a "user unknown" message? Does anyone do this? Hell I never even thought of doing this. This is absolutely insane! Every domain every day loses a few email names due to natural attrition and closed accounts. So if I get one, I;'m supposed to STOP mailing that domain? Again, who does this? Is this IP address configured as if the associated machine was infected by a virus? We need clarification on this, exactly what is she asking here? An .info domain with no RDNS or DK/DKIM = virus infected bot net machine? Is this IP address listed on blocklists we use? Probably the one question here that makes any sense. Please run these questions filling in your own answers and share... I'm curious if anyone is doing all the above 100%.