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Why are my emails going to spam?

By Alexander Rosales · Updated 26 October 2026

Short answer: in the audits I've run, it was almost never the words in the email. It was the domain, the inbox, the list or the tracking. Here are the causes in the order I check them, with the numbers I measured, and what to do about each one.

1. Your authentication is missing or doesn't line up

SPF, DKIM and DMARC tell Gmail and Microsoft that you are allowed to send from your domain. If one is missing, or if the domain they vouch for doesn't match the address in your From line, many inboxes treat the email as suspicious before reading a word of it.

The mistakes I see most: two SPF records on the same domain (both stop working), SPF that needs more than 10 DNS lookups, DKIM never switched on in the sending tool, and no DMARC record at all.

You can check all four records in about ten seconds with the free deliverability checker. But if everything passes, keep reading: in one audit, SPF, DKIM and DMARC passed on all 67 sending domains, and the mail still went to spam.

2. Your sending domains are worn out

Sending domains lasted about 2 to 3 months before they started burning.

That was the main finding of an audit for a B2B team with 67 active sending domains. On the newest batch, Gmail inbox placement fell from 20 of 20 seed inboxes in early October to 7 of 21 a few weeks later. Earlier in the year, the same copy sent to the same leads on the same day got a 2.90% reply rate from new inboxes and 1.71% from old ones.

What to do: replace sending domains on a schedule, before replies collapse, and keep a few new ones warming in reserve so you never send from a tired domain because it's the only one you have.

3. Bounces are burning your reputation

Catch-all addresses bounced at 4.19%. Verified ones at 1.09%.

That's from 838 of my own sends. A catch-all domain accepts any address when you verify it, so the checker says "maybe", and the real bounce arrives later. In the 67-domain audit, bounces reached 4.23% in the second half of April. Two weeks later, replies had fallen to 0.44%.

What to do: verify every address before it goes into a campaign, keep catch-alls out or in a separate, small campaign, and pause any campaign whose bounce rate climbs past 2 to 3%.

4. The open-tracking pixel

Microsoft 365 and Proofpoint flagged the email only with the pixel on.

In seed-inbox tests in October 2026, the same email passed both filters with open tracking off and was flagged with it on. The pixel is a tiny remote image with a tracking link, which is exactly what corporate filters are built to distrust, and many business buyers sit behind Microsoft 365 or Proofpoint.

What to do: turn open tracking off for cold email and measure replies instead. Opens were never a reliable number anyway, since some filters open the email automatically before a person does.

5. Too much volume per inbox

Every inbox has a pace it can sustain. In the 67-domain audit, about 6 cold emails per inbox per day was a safe level for that setup. My own sending platform never goes above 30 per inbox per day, with a gap of several minutes between sends.

What to do: add inboxes instead of pushing each one harder, and ramp new inboxes up slowly after warm-up.

6. A link or domain inside your email is on a blocklist

This one happened to me. My emails started bouncing with "550 An URL in this email is listed by Spamhaus DBL". My own domain was clean. The listed one was the domain inside the tracking links: a shared hosting domain that someone else had abused. Moving tracking to a domain of my own fixed it.

What to do: check every domain your email touches, not just the one you send from. That means links, tracking, images and the signature, against Spamhaus and SURBL.

7. You send cold email from your main domain

Even if it works today, it puts everything on one bet. When that domain gets flagged, your invoices, support replies and password resets go to spam with it. Send cold email from separate domains in your name, and point those domains to your website so anyone who checks them sees a real business.

8. Last: the copy

Own copy: 21.5% inbox. Neutral copy: 19.0%.

Same domains, same day, seed-inbox test. Rewriting the email changed nothing, because the problem was never the words. Copy matters for replies; for placement it comes after everything above.

Google Workspace emails going to spam?

Everything above applies, plus one trap. Google Postmaster Tools only shows reputation for domains that send enough volume. Cold email domains often send too little to show any data, so Postmaster stays silent while placement drops. Seed-inbox tests catch it earlier.

What to do this week

1. Run your sending domains through the free checker and fix any red result.
2. Turn off open tracking on every cold campaign.
3. Verify your lists and move catch-all addresses out.
4. Write down the age of every sending domain and plan its replacement.
5. Check every domain inside your links and tracking against Spamhaus and SURBL.