Why emails go to spam and how to fix it in 30 minutes

Emails usually land in spam for three reasons: the domain has no SPF, DKIM and DMARC records, the inbox is new and starts sending a lot at once, or the list has many addresses that don't exist. You can check and fix all of this in half an hour. Here's how, step by step, with our own experience.

Our case: sign-up emails went to spam

When we launched Vibe Hunters, the first sign-up confirmation emails went straight to spam. Awkward for a product that helps people send email. The reason was mundane: the domain had no proper SPF, DKIM and DMARC records, and emails were sent directly instead of through a mail service.

After the setup described below, our mail-tester score went up to 9.2 out of 10 and the emails started arriving in the inbox.

Reason 1. No SPF, DKIM and DMARC

Since 2024 Gmail and Yahoo require authentication from every sender, and DMARC from anyone sending over 5,000 emails a day. Without these records a mail provider can't confirm the email really comes from you.

• SPF is a TXT record in your domain's DNS listing the servers allowed to send mail on your behalf, for example v=spf1 include:_spf.google.com ~all for Google Workspace.
• DKIM is a digital signature on each email. Your mail service (Google Workspace, Microsoft 365, Brevo and so on) generates the key, and you add it to DNS.
• DMARC is the rule for emails that fail SPF or DKIM. Start soft: v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com.

You add these records at your domain registrar or wherever your DNS is managed. Changes usually take effect within an hour. The full walkthrough with examples is in SPF, DKIM and DMARC explained.

Reason 2. A new inbox sends hundreds of emails at once

Mail providers trust addresses with a history. An inbox created yesterday that sends 300 identical emails to strangers today looks like a spammer.

What to do:

• start with 10–20 emails a day and increase gradually over two to four weeks;
• keep to 30–50 cold emails a day per inbox, and add inboxes for more volume;
• leave pauses between emails instead of sending everything in a minute.

Google lists a limit of around 500 emails a day for regular Gmail and 2,000 for Workspace, but that's a technical ceiling, not a safe pace for cold email.

Reason 3. Dead addresses in your list

Every email to an address that doesn't exist comes back as a bounce. Many bounces tell mail providers you're sending to a bought or outdated list. Keep bounces below 2–3%.

Check addresses before sending: does the domain exist, does it accept mail, does the mailbox itself exist. More on that on our email verification page.

Reason 4. The email copy

The text itself is a less common cause than technical setup, but it still matters:

• several links and an attachment in a first email from an unknown address;
• words like "FREE!!!", caps lock, rows of exclamation marks;
• an email that's just an image with no text;
• hundreds of identical emails in a row.

Write like a person writing to a person: short, few links, varied phrasing. There are examples in cold email templates.

Reason 5. "Report spam" complaints

Google recommends keeping the complaint rate below 0.1%; above 0.3% emails go to spam at scale. Complaints come when an email is irrelevant or hard to unsubscribe from.

Write to people your offer can genuinely help, and always give an easy way to opt out.

The 30-minute checklist

1. 5 minutes. Send an email to the address from mail-tester.com and look at the score and the list of issues.
2. 10 minutes. Add or fix SPF, DKIM and DMARC in your domain's DNS.
3. 5 minutes. Make sure your emails carry valid Date and Message-ID headers; if you send from your own code, they're often forgotten.
4. 5 minutes. Cut the daily volume per inbox to 30–50 emails and add pauses.
5. 5 minutes. Run your list through an address check and remove invalid ones.

Then send another email to mail-tester. A score of 8 or more means the technical side is fine, and from there deliverability depends on who you write to and what you say.