Why Do My Emails Go to Spam? Deliverability Checklist

Emails landing in spam - or not arriving at all - almost always come down to a few technical checks that Gmail, Outlook and other providers run on every message. Work through this checklist from top to bottom; most problems are fixed by the first four steps.

Quick test first: send an email to mail-tester.com - it checks most of the items below in one go. See Test your mail setup.

1. SPF - Is Your Server Allowed to Send?​

SPF is a TXT record listing which servers may send email for your domain. OpenPanel creates one automatically when you add a domain:

example.com.   TXT   "v=spf1 ip4:203.0.113.10 +a +mx ~all"

Check:

• There is exactly one SPF record per domain (two records = SPF fails).
• It contains your server IP, plus every other service that sends as your domain (Google Workspace, newsletter tools, SMTP relay) via include:.
• If your DNS is hosted elsewhere (Cloudflare, registrar), the record exists there.

See Add additional hosts to SPF.

2. DKIM - Is Your Email Signed?​

DKIM adds a cryptographic signature to every message, verified with a public key in DNS (mail._domainkey.example.com). Without it, Gmail and Outlook trust your email much less.

See Set up DKIM.

3. DMARC - Do You Have a Policy?​

DMARC ties SPF and DKIM to the From: address and tells receivers what to do with failures. Gmail and Yahoo require it for bulk senders. OpenPanel adds a basic p=none record for every domain.

See Set up DMARC.

4. Reverse DNS (PTR) and Hostname​

The server's IP must resolve back to its hostname, and the mail server must introduce itself with that same hostname:

203.0.113.10 → PTR → server.example.com → A → 203.0.113.10

• Set a domain for the server in OpenAdmin → Settings → General - it's also used as the mail server hostname.
• Set the PTR record at your hosting provider.

See Set up reverse DNS (PTR).

5. Check Blocklists​

If your server IP (or domain) is on a spam blocklist, many providers reject or filter your email.

• Check the IP at MXToolbox Blacklist Check or multirbl.valli.org.
• Find out why it was listed first - usually a hacked website or mailbox sending spam. Check the mail queue in OpenAdmin (Emails → Queue) for unusual volumes, and scan sites for malware (ImunifyAV).
• Then request delisting on each blocklist's website.
• New cloud IPs are sometimes listed from a previous owner - ask your provider for a clean IP, or use an SMTP relay.

For Microsoft (Outlook, Hotmail) delivery problems, use the Microsoft Sender Support form; for Gmail, register with Google Postmaster Tools.

6. Is Port 25 Open?​

If emails don't arrive at all (not even in spam) and sit in the queue, your provider may block outgoing port 25. See Port 25 blocked: use an SMTP relay.

7. Content and Sending Behaviour​

With a correct technical setup, remaining spam-folder problems are usually about content and reputation:

• Warm up a new server or domain - start with small volumes and increase gradually.
• Don't send newsletters or bulk mail from your web server; use a dedicated email marketing service.
• Include a plain-text version, a real From name, and an unsubscribe link for newsletters.
• Avoid URL shorteners, all-caps subjects, large images with little text, and attachments like .zip or .exe.
• Make sure the From address is on your own domain - sending "from" @gmail.com through your server always fails DMARC.
• Websites should send through an authenticated mailbox (SMTP) on the site's own domain, not anonymous PHP mail().

8. Using an External DNS Provider?​

If your domain's nameservers point to Cloudflare, your registrar or another DNS host, OpenPanel's DNS zone isn't used. Copy the SPF, DKIM, DMARC and MX records from OpenPanel → Domains → DNS to your DNS provider. With Cloudflare, mail hostnames must be DNS only (grey cloud) - see Use Cloudflare with OpenPanel.

Checklist Summary​

• One SPF record including the server IP and all senders
• DKIM key published and messages signed
• DMARC record published
• Server domain set; PTR record matches it
• IP and domain not on blocklists
• Outgoing port 25 open, or relay configured
• mail-tester score 9/10 or higher

Related​

• Troubleshooting email errors
• Set up email clients
• Enable email hosting