My company has a weekly newsletter with lists of available homes in the recipient's market that's been going out for years in the same format. Because of the short timeframe at which people are interested in buying a new home, the open rates for recipients tapers off after a few weeks/months of being subscribed.

I've heard from many sources that removing people from regular mailings who haven't engaged with your brand in a while is a good practice, as email providers like to see active lists. Following that principle we began systematically removing folks who weren't active (opened/clicked) in the past 90 days.

However after putting this removal practice in place, we found that the response rates on the emails actually decreased when that should be mathematically impossible -- the open/click rates should have sharply increased with the removed dead weight. But over the past 2 years we've seen this happen in two ESPs with a variety of list types and email formats.

Has anyone run into this issue before? My best guess is that Google, MS, etc. are only allowing a portion of our email traffic through and by sending less we are not getting as many emails through. I appreciate any insight anyone has on this.