DFY GTM Systems

How to Avoid Spam Filters

By Abdul Sami, GTM Engineer · 6 min read · Last updated

Avoiding spam filters in 2026: authenticate (SPF/DKIM/DMARC), warm up new infrastructure 2–4 weeks, keep hard bounces under 2% and complaints under 0.1%, send plain-text-style emails with at most one link, vary your copy, and keep volume per mailbox under 25–30/day.

The technical checklist

  • SPF: one record, -all policy, under 10 lookups.
  • DKIM: 2048-bit, signing enabled, not just DNS-published.
  • DMARC: enforced (quarantine or reject), rua reporting on.
  • Custom tracking domain or open tracking off shared tracking domains carry other people's reputation.

The sending checklist

  • Warm up 2–4 weeks before cold volume.
  • 25–30 emails/day/mailbox ceiling.
  • Verified lists only; bounces under 2%.
  • Unsubscribe honored instantly complaints are the heaviest negative signal.

The content checklist

  • 0–1 links, no attachments on first touches.
  • No image-only emails; minimal HTML.
  • Avoid classic trigger phrases ('free', 'guarantee', 'act now').
  • Vary copy with spintax; identical blasts pattern-match to bulk mail.

When you're already in spam

Stop sending from the affected domain. Diagnose (blacklist? complaints? authentication break?), fix the root cause, rest the domain 2–4 weeks, then re-warm. Sending through a spam problem only deepens it.

FAQ

What triggers spam filters most?
Recipient behavior signals (complaints, no engagement, deletes) outweigh content. Technically: missing authentication, unwarmed volume spikes, and bad lists are the top controllable triggers.
Do spam trigger words still matter?
As one layer among many. Clean copy on a burned domain still lands in spam; risky copy on a great domain often lands fine. Fix infrastructure first, copy second then run the Spam Checker.
Should I turn off open tracking?
For cold email, often yes the tracking pixel uses a shared domain and adds HTML weight. Many top senders track replies only. Test both on your own infrastructure.
AS

Abdul Sami

GTM Engineer, DFY GTM Systems

7+ years building outbound systems for B2B companies across the US, UK, Australia, and DACH. Specializes in Clay workflows, cold email infrastructure, intent-based lead sourcing, and deliverability.

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