Email deliverability is no longer just about avoiding spam keywords. In 2026, mailbox providers evaluate sender reputation using behavioral signals, authentication strictness, complaint rates, and engagement quality.
If your emails aren’t landing in the inbox, it’s usually not random — it’s reputation.
This guide breaks down the most effective modern deliverability strategies.
Authentication is the foundation of trust.
Minimum required setup:
Move DMARC from monitoring (p=none) to enforcement (quarantine or reject) once validated. Strong authentication signals legitimacy.
New sending domains are treated cautiously by mailbox providers.
Best practice:
Sudden spikes damage trust immediately.
List hygiene directly affects sender reputation.
Remove:
Engagement quality matters more than list size.
Spam complaints are one of the strongest negative signals.
Aim for:
Reducing friction reduces complaints.
Transactional emails (password resets, receipts) should not share reputation with marketing campaigns.
Use:
Isolation protects critical flows.
DMARC reports reveal:
Treat these reports as operational intelligence.
Changing:
All at once can trigger filtering systems. Make changes gradually and monitor impact.
Deliverability is earned over time. It requires consistency, authentication discipline, list hygiene, and monitoring.
Think of reputation like credit — slow to build, easy to damage.
Treat it as infrastructure, not marketing.