First, confirm the problem
Before changing anything, make sure you are looking at a real pattern. A single report that “your email went to spam” may reflect one person’s settings. Look for signs across many recipients: low open numbers compared with your usual results, replies from people saying they found you in junk, or test messages arriving in spam at several providers.
Test by sending to a few personal inboxes at different providers, such as Gmail, Outlook and Yahoo, and see where each message lands. Note whether the problem affects one provider or all of them, since this changes where you should look. Open figures alone are a weak guide, because some mail apps hide or inflate opens.
Spam filtering is decided by the receiving provider using many signals that are not published, so no checklist can promise a fix. What follows are the causes most often given, in a sensible order of investigation.
1. Authentication
Check that SPF and DKIM pass and that a DMARC record exists. Missing or broken records are among the first things to rule out, particularly after changing email service, web host or domain settings. Your email service often has a checker, or you can read the headers of a received test message. The article on SPF, DKIM and DMARC explains what to look for.
2. Sender reputation
If authentication is fine, consider your history. Have complaints, bounces or unsubscribes risen lately? Did you send a big campaign after a long gap, or increase volume quickly? A new domain that skipped domain warm-up is a very common culprit. Providers judge you over time, so a recent change in behaviour may explain a sudden change in placement.
3. List quality
Ask where your addresses came from. Spam placement often follows:
- Mailing an old list that has not been cleaned in a long time.
- Purchased, rented or scraped addresses.
- Importing contacts who never agreed to marketing email.
- A high rate of bounces, which a routine of list hygiene is meant to prevent.
- Large numbers of long-inactive subscribers who never open.
Sending only to people who opted in is the strongest protection. Marketing consent rules vary by country and change over time, so check what applies to you; this is general information, not legal advice.
4. Complaints and unsubscribes
If recipients cannot easily leave, some will press the spam button. Check that your unsubscribe link is visible and works, and that requests are honoured quickly. A hidden or broken opt-out can turn quiet disinterest into complaints.
5. Content
Content is usually less decisive than reputation and list quality, but some patterns draw attention. Review these:
- Subject lines: Misleading claims, fake “Re:” or “Fwd:” prefixes, all capitals, or heavy punctuation. If you test alternatives, keep the test fair; see subject line testing for how.
- Body copy: Exaggerated promises, pressure language or a lot of sales wording with little useful information. Honest advertising is good for readers and for filtering.
- Images: Messages that are one large image with almost no text can look suspicious. Include real text, and use alt text for images, which also helps accessible email.
- Links: Too many links, links that do not match the visible text, link shorteners and links to domains with a poor record. Make sure the links go where they say.
- Attachments: Unexpected attachments, especially certain file types, can trigger filters. Link to a file on your site instead where practical.
- Formatting: Broken HTML, a missing plain-text version, or odd formatting.
- Identity: A recognisable sender name, a real reply address, and the business details your local rules require.
Do not treat old “spam word” lists as a rulebook. Modern filters rarely rely on single words, and avoiding a word may do little. Write plainly and honestly.
6. Sending patterns
Look at how you send. A sudden jump in volume, an irregular rhythm, or a big blast from a shared address can all look unusual. If you use a shared sending address through your email service, other customers’ behaviour may affect you; consult your service’s guidance.
Also check the From address. A free webmail address used for bulk marketing, or a From domain that differs from the domain in your authentication, can cause trouble.
7. Technical hygiene
Make sure your domain and website look legitimate: a working site, a privacy notice, and consistent business details. Check that links point to HTTPS pages that load properly. Make sure your reply address can receive mail.
What probably does not matter much
- Using the word “free” once in a sentence, in a genuine context.
- Having an emoji in a subject line, in itself.
- Small differences in message length.
Beyond these, chasing guesses can waste time. It is better to fix the large factors first.
A suggested order of work
- Confirm the pattern across providers.
- Check authentication.
- Review recent volume and list changes.
- Check bounce and complaint figures in your email metrics.
- Send a smaller campaign to your most engaged subscribers and see whether placement improves.
- Review content and links, one change at a time.
- Ask a few subscribers to move your message to the inbox or reply to it, which is generally regarded as a positive signal. Never pressure people or use deceptive prompts.
Be patient. If your reputation has been damaged, placement usually recovers gradually and not instantly. Outcomes vary, and the rules of mailbox providers change, so check their current documentation and that of your email service.