Mark Brownlow has a list of 12 questions every email marketer should ask about their marketing program. Buried in the middle is the most important question for delivery.
Do you worry more about what ISPs think about your email than what subscribers think about your email? If you take care of the latter, won’t the former take care of itself?
My answer is if a sender is worried more about what the ISPs think than what subscribers think that sender is going to have ongoing and continual delivery problem. However, if a sender focuses on sending relevant, expected and wanted email then they will have almost zero delivery problems.