A friend of mine called to pick my brain on email marketing. His company has about 70,000 subscribers and their open rates were getting WORSE with each new campaign.
In his testing, he saw that a lot of their emails were getting delivered to the spam folder. He was looking for changes they could make to improve their deliverability.
I explained that consistently getting into the inbox was based on their email reputation. Their email reputation is based on their subscriber engagement. In a nutshell, when a company sends out an email, the email providers (Yahoo, Gmail, etc.) consider the following behaviors, which negatively affect your reputation: