What are the main factors that affect email deliverability?

Deliverability rests on four pillars: authentication, reputation, engagement, and list hygiene.

Authentication proves your identity using SPF, DKIM, and DMARC. Reputation reflects how trustworthy your sending history is based on bounces, spam complaints, and consistency. Engagement tells mailbox providers whether their users value your mail. List hygiene ensures that you only send to active, permission based contacts.

Together these pillars act like a set of lighthouses guiding your ship safely through inbox waters.