A few resources that may help make sense of the many factors affecting email deliverability.
- It's a Bird, It's a Plane, It's Email Deliverability by Courtney Sembler of HubSpot Academy (5 min Read)
- Understanding Email Deliverability -- Community Articles
- Understanding Email Deliverability -- Knowledge Base
Good To Know
- Email Bounces and how they affect contact eligibility
- How can I improve the deliverability of my emails?
The following big dogs are responsible for sending / testing over 25% of the world's non-spam email, so should probably consider anything on their radar a priority concern.
- - see 15 Email Deliverability Best Practices for Gmail (SparkPost)
- - see Make It to the Inbox—Not the Spam Folder—with Litmus Spam Testing (Litmus)
- - see Top Tips to Avoid Spam Filters When Sending Emails (SendGrid)
- - see How to Avoid Spam Filters (MailChimp)
- - see A Marketer's Guide to Email Deliverability: How to Avoid Email Spam Filters (HubSpot)
As a side note, SparkPost also has some excellent information about ramping up sends to large lists (>1M contacts) and warming up sends to lists in general. Just excellent stuff every email marketer should indelibly impress in their brains.