Mailbox providers use the number of messages delivered to their customers' inboxes to determine an IP address's complaint rate. When a high volume of mail from an IP address is being delivered to the inbox, it takes a larger number of complaints to raise your complaint rate.
Subscribers do not necessarily complain on the day an email is sent, so complaints can come in for a campaign days or even weeks after the initial send. If the volume from an IP address has decreased during that time, that can potentially inflate your complaint rate.
Example: An IP address sends 100,000 messages on Tuesday. That volume is counted on Tuesday. 100 subscribers read the message on Tuesday and complain. Therefore, for Tuesday, the IP has a complaint rate of .001. On Wednesday, that same IP address sends 100 messages. None of the subscribers to that message complain; however, 100 subscribers to the message sent Tuesday do complain. Because those complaints were received Wednesday, they are counted against Wednesday's volume, resulting in a complaint rate of 100%.
Reputation
