Key takeaway: Most cold emails are not flagged for one dramatic reason. They are flagged for four or five small ones stacked together. Run this checklist before every campaign goes out.

Most cold emails do not get flagged for a single glaring mistake. They get flagged for a cluster of small ones. Work through these before you hit send.

Authentication and infrastructure

• SPF, DKIM, and DMARC all present and passing. Send a test to Gmail, open "Show original," and confirm three PASS results.

• Sending from a secondary domain, never your primary company domain.

• Two to three inboxes per domain, not ten.

• Every inbox warmed for at least two weeks before real sends.

• Sending domain redirects to a real, live website.

The email itself

• Plain text style. No heavy HTML templates, no image banners, no brand headers.

• One link maximum. No shortened URLs, since bit.ly and similar are heavily abused and heavily filtered.

• No tracking pixel on a shared tracking domain. Use a custom one or turn open tracking off.

• No attachments. Ever, on a cold email.

• Formatting stays human: no ALL CAPS, no exclamation stacks, no colored or oversized text.

Language that gets you filtered

Filters are not fooled by "FR£E" spelling tricks, but they do score aggressive sales language. Watch for: free, guarantee, risk free, act now, limited time, click here, buy, order, cash, income, earn, winner, urgent, congratulations. One will not sink you. A cluster will.

List and behavior

• List verified immediately before sending, with bounce rate under 2 percent.

• No purchased or scraped lists that have not been verified.

• Sends spread across many inboxes at low volume each, not blasted from one.

• Random delays between sends, not perfectly spaced intervals.

• A clear, easy opt out. Making it hard to unsubscribe generates spam complaints, the most damaging signal you can collect.

Before you hit send

• Run your copy through a spam checker first. Our free spam checker flags the trigger words and formatting that get you filtered.

• Seed test to a spread of Gmail and Outlook inboxes and check actual placement.

• Preview on mobile, since most cold email is read there first.

• Subject line is short, lowercase, and reads like a person wrote it.

If you can tick every box, you have eliminated the things you control. What remains is copy and targeting, which is a much better problem to have than a spam folder.

Frostmailer mailboxes ship with the authentication and infrastructure boxes already ticked: secondary domains, SPF, DKIM, and DMARC configured and verified, redirects in place, and warm-up done. That leaves you the copy and the list, which is where your time actually moves the needle.

Want this done for you?

Our Build and Release service stands up your entire cold email infrastructure: domains, mailboxes, authentication, warm-up, and tracking, all authenticated and ready to send. You skip the weeks of setup and start with campaigns.

Book a call