DeliverabilitySpam

Why Your Cold Emails Are Going to Spam (and How to Find the Real Reason)

Nestmarketing Team · · 3 min read

Almost every week someone messages us with the same line: "Our emails were fine last month. Now everything is in spam." Then they ask which word in their email is the problem.

It is almost never a word.

When cold email lands in spam, the cause usually sits in one of five places. The trick is to check them in the right order, because the first two can make everything else irrelevant.

1. Authentication

Before Gmail or Outlook reads a single word, they check whether you are allowed to send for your domain. That means SPF, DKIM and DMARC.

Open any email you sent to a Gmail address, click the three dots and choose Show original. You want to see:

  • SPF: PASS
  • DKIM: PASS
  • DMARC: PASS

If any of these say FAIL or NONE, stop here and fix it. Nothing else matters until they pass. We wrote a separate guide on setting up SPF, DKIM, DMARC and BIMI, and another on the confusing case where SPF and DKIM pass but DMARC still fails.

2. Domain and IP reputation

Mailbox providers keep a score for your sending domain and IP. You can't see it directly, but you can see the symptoms:

A brand-new domain has no reputation at all, which is nearly as bad as a poor one. If the domain is under a month old and you started sending at full volume, that alone explains the spam folder. Warm-up exists for exactly this reason.

3. List quality

This is the one people least want to hear. If your bounce rate is above 2 to 3%, providers read it as "this sender bought a list" and adjust accordingly.

Bad lists also carry spam traps: addresses that exist only to catch senders who don't clean their data. A handful of trap hits can sink a domain. We explain how spam traps end up on your list and how to bring bounce rates down in separate posts.

4. Sending pattern

Humans don't send 400 emails at 9:00:00 AM sharp. They also don't send 50 one day and 900 the next.

Things that look automated to a filter:

  • Big bursts at the same minute
  • Daily volume that jumps around
  • Too many emails per mailbox (we keep cold mailboxes at 30 to 50 a day; here's the maths)
  • Every email in a campaign being identical

5. Content

Only now do we look at the email itself. Content problems are real but usually smaller than people think. The common ones:

  • Link shorteners like bit.ly
  • Several links, or links to a domain with a bad history
  • Open tracking on a shared tracking domain (fix with a custom tracking domain)
  • Heavy HTML, images or attachments in a first-touch email

Spam "trigger words" matter far less than the internet suggests. We wrote a whole post on that myth.

How to test properly

Sending a test to your own Gmail tells you very little, because your own inbox knows you. Use a seed-list placement test across Gmail, Outlook, Yahoo and a few business mail servers. Our guide to inbox placement testing walks through it.

The short version

Check in this order: authentication, reputation, list, sending pattern, content. Most teams start at the bottom of that list and spend weeks rewriting emails that were never the problem.

If you want a second pair of eyes, send us a message. We will look at your headers, DNS and sending setup and tell you what we see, free of charge.

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