It’s pretty well established by deliverability lore that complaint rates do matter for inbox placement. However, I haven’t seen good quantification of where the thresholds for good vs. bad delivery rates are. My colleague John Young and I pulled together some sample analysis to see if it was possible to quantify complaint thresholds at two different ISPs: AOL and Yahoo.
Yep, complaint rates really do matter.
We took a look at the complaint rates from the Sender Score Reputation Network for IP addresses that had been mailed into our delivery monitoring tool, Mailbox Monitor. The complaint data comes from about 20 ISPs, hosting companies and security providers that are part of our network. The inbox placement data is from the over 1,000 customers that currently use Mailbox Monitor (we eliminated those campaigns that had been sent from multiple IPs).
The graph below shows you what we found:
The next steps in our analysis will be to extend this analysis to other ISPs and to look at the other factors that we know to cause delivery issues: spam traps, blacklists, high unknown user rates and volume patterns.