How to test email deliverability (avoid the spam folder)

Updated 10/16/2026

A mail server that sends correctly on the technical side can still land in spam if reputation or configuration are not good. Here is how to test.

1. The Gmail test

Send an email to a Gmail account, open it, click the three dots, "Show original". Check:

SPF: PASS
DKIM: PASS
DMARC: PASS

If any is "FAIL", fix it, see SPF, DKIM and DMARC.

2. Spam score tools

There are free online services where you send a test email and get a detailed score (authentication, content, blacklists). A good score increases your chances of reaching the inbox.

3. Check reverse DNS

dig -x SERVER_IP +short

It must return the mail server's name, see reverse DNS.

4. Check blacklists

Make sure your IP is not on blocklists, see How to check if you are on a blacklist.

IP warmup

A new IP should send small volumes at first, increasing gradually, to build reputation.

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