Does this match what you’re seeing?
- Recipients find your messages in junk or spam
- Gmail shows a warning banner on your messages
- Replies to your emails never come
Spam filters score each message on many signals. Fix the ones you control, roughly in this order of impact.
1. Authentication (fix this first)
Missing or failing SPF, DKIM or DMARC is the most common cause, and Gmail and Outlook increasingly reject or junk unauthenticated mail.
Send a test to a Gmail address, open it, choose Show original, and check:
SPF: PASSDKIM: PASSwith your domainDMARC: PASS
Anything else: SPF, DKIM and DMARC explained.
2. How the message is sent
- From a website using PHP’s basic mail function, often with a From address the server doesn’t authenticate? Switch to authenticated SMTP. Sending email from your website reliably
- From Gmail’s servers while using your domain address? That fails SPF. Send through your own server.
3. Content
- Avoid a single large image with little text
- Avoid link shorteners and links to domains with bad reputations
- Write a real subject line, not “Hi” or all capitals
- Include a plain-text version for newsletters
4. Reputation
- Blocklists: check whether the sending IP or your domain is listed. Email blacklists (blocklists): how to check and what to do
- A new domain has no reputation; start with normal person-to-person mail.
- A compromised account sending spam damages reputation fast. My email account is sending spam
5. Recipient behaviour
If recipients rarely open, delete without reading or mark messages as spam, providers learn to file them away. Only send mail people expect.
6. Bulk email
Newsletters and marketing mail should go through a dedicated email marketing service with its own infrastructure and unsubscribe handling. Getting email delivered to Gmail and Outlook
Quick test
Ask a recipient who found your mail in spam to mark it Not spam and add you to contacts. It helps that recipient immediately, but only fixing the causes above helps everyone else.