Email deliverability and spam filters: what teams need to fix

TL;DR: Emails usually land in spam because of fixable issues such as weak authentication, poor sender reputation, low engagement, or spam-like content, not random chance, according to Valimail. Inbox placement now depends on governance over identity signals, sending behaviour, and provider requirements, not just message quality.

Editorial analysis by NHI Mgmt Group, based on content published by Valimail: “Why your emails go to spam: 8 fixes that work”.

By the numbers:

• Spam complaints should stay below 0.1%, and they should never reach 0.3%.

Key questions

Q: How should organisations reduce legitimate emails being flagged as spam?

A: Start by fixing authentication, sender reputation, and audience hygiene together.

Q: Why do authenticated emails still end up in spam or get blocked?

A: Authentication proves origin, but it does not override mailbox policy.

Q: What are the signs that email deliverability controls are failing in practice?

A: Common signals include rising hard bounces, spam folder placement, unexplained silence after accepted delivery, suppression list hits, and poor reputation indicators in postmaster tools.

Practitioner guidance

• Implement SPF, DKIM, and DMARC alignment Validate every sending domain and subdomain, then confirm that authentication alignment holds across all mail streams and third-party senders.
• Reduce complaint-driven reputation damage Audit complaint rates, remove disengaged recipients, and stop sending to audiences that repeatedly mark mail as spam.
• Normalise sending patterns Avoid sudden spikes, abrupt drops, and erratic campaign bursts so provider heuristics do not interpret the traffic as suspicious.

Bottom line: Email spam placement usually reflects weak trust signals, not random failure.

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