Factors affecting email deliverability

Recently major email providers made changes to the rules around email deliverability. Gmail, Yahoo, and Outlook now examine sender reputation closely and have made significant updates to their spam filters.
Factors That Affect Your Email Deliverability:
Excessive Spam Complaints
Spam complaints are reported by real human beings who are recipients of your email marketing. They do this by marking that the message is Spam/Junk to the email provider directly in their inbox or when they opt-out of marketing and say this is spam. A Spam complaint is Not a Spam trap. The industry limit for a spam complaint rate is 1 complaint for every 1000 emails sent per email service provider (ESP) or .100% per ESP. Your goal is to be below the .100 per provider.
Percentage of Email Categorized as Spam Due to Sending Practices
This is the predicted percentage of your emails that 3rd party email monitoring services have categorized as spam based on your overall email sending practices. Items that can affect this are content, domain reputation, engagement and complaint feedback. This is not a Spam complaint metric.

Average Engagement Days
This metric is based on all the contacts you have sent email to in the last 30 days and the average days since they last engaged with your marketing. Engagement is tracked by opening an email, clicking in an email, or submitting a webform. The email marketing industry recommend this number be less than 60 days.

Supplemental Data: Low Open Rates
This is the percentage of your email marketing that the recipients opened the email. The current industry average for open rate is 17.92%The measurement is for informational purposes only and Not used for compliance. Cold email lists will typically underperform warm "house" lists.