Reviewed by the NexaToolkit team · Last reviewed June 2026. Updated for the Feb 2026 bulk-sender rules that changed deliverability for everyone. NexaToolkit may earn a commission from links on this page — it never changes what we recommend.
Email deliverability got harder in 2026: after Google and Microsoft tightened bulk-sender rules in February, senders without proper authentication saw inbox placement collapse. The good news — deliverability is now mostly about doing a few technical things correctly, not luck. Here’s the practical playbook, with the tools that check each box.
Step 1: authenticate (SPF, DKIM, DMARC) — non-negotiable now
The Feb 2026 rules made SPF, DKIM, and DMARC mandatory for bulk senders — without them, you go to spam or get rejected. Set all three on your sending domain; tools like MXToolbox (free checks) and your ESP’s domain wizard verify them. This is the single biggest lever.
Step 2: warm up new domains and IPs
Never blast from a cold domain. Warmup tools — built into Instantly and Smartlead, or standalone — gradually ramp sending volume so mailbox providers build trust. Critical for cold outreach and new sending domains.
Step 3: keep your list clean
Sending to dead addresses tanks your reputation. Verify with ZeroBounce or NeverBounce before importing, and prune unengaged subscribers regularly — a smaller engaged list beats a big stale one for placement.
Step 4: monitor reputation and engagement
Watch Google Postmaster Tools (free) for your domain reputation and spam-complaint rate, and keep complaint rates under the 0.3% threshold the new rules enforce. Falling open rates are an early warning — act before placement drops.
The deliverability checklist
| Step | What to do | Tool |
|---|---|---|
| Authenticate | SPF + DKIM + DMARC | MXToolbox, ESP wizard |
| Warm up | Ramp new domain/IP volume | Instantly / Smartlead |
| Clean list | Verify + prune dead emails | ZeroBounce / NeverBounce |
| Monitor | Reputation + complaint rate | Google Postmaster Tools (free) |
A real scenario
A business whose open rates suddenly dropped in 2026: first, confirm SPF/DKIM/DMARC are all set (MXToolbox, free) — post-February, missing DMARC alone can route everything to spam. Then verify the list with ZeroBounce, prune anyone who hasn’t opened in 90 days, and watch Google Postmaster Tools to confirm reputation recovers. Most “deliverability problems” in 2026 are just missing authentication — fix that first and placement usually returns.
Frequently asked questions
How do I improve email deliverability?
Four steps: set SPF + DKIM + DMARC (mandatory since Feb 2026), warm up new sending domains, keep your list clean (verify + prune), and monitor reputation via Google Postmaster Tools. Authentication is the biggest lever.
What changed for email senders in 2026?
Google and Microsoft made authentication (SPF/DKIM/DMARC) mandatory for bulk senders and enforce a spam-complaint rate under 0.3%. Senders without proper setup saw inbox placement collapse.
Why are my emails going to spam?
Most often missing authentication (especially DMARC) post-February 2026, a dirty list with dead addresses, or a cold domain sent at high volume without warmup. Fix authentication first.
More: see our cold email software and transactional email services.
