Why are my emails going to spam? A diagnostic for online stores

Fix-it checklist#

1. 1

   Confirm authentication passes

   Send a test to a Gmail address and open the message details. Your own domain should appear next to “mailed-by” and “signed-by” ^S2. If not, fix SPF, DKIM and DMARC before anything else.

2. 2

   Pause sends to cold contacts

   Stop emailing addresses that have not opened or clicked in months, anyone who did not sign up, and every address that bounced.

3. 3

   Make leaving easy

   Add one-click unsubscribe headers and a visible unsubscribe link, and remove people who unsubscribe within two days ^S6.

4. 4

   Restart with your most engaged customers

   Send the next campaign to recent buyers and recent clickers only, then widen the audience over several sends ^S1.

5. 5

   Watch the numbers for two weeks

   Track the spam rate in Google Postmaster Tools and keep it below 0.10% ^S1S3.

How inbox filters decide#

Mailbox providers such as Gmail, Yahoo and Outlook do not judge an email on its words alone. They ask three questions: is the sender who it claims to be, how have this sender’s recipients reacted before, and does this message look like what those recipients asked for. A spam folder problem is almost always an answer of “no” to one of them.

That is why the useful approach is diagnostic. Start with causes you can confirm in minutes, then move to the slower ones. The order below is ranked by how quickly you can check each cause, not by how often it occurs. If you have never set up a sending domain, read email deliverability basics first; this page assumes you are already sending and something has gone wrong.

Seven causes and how to check each one#

1. Authentication fails or does not align

Gmail requires every sender to pass SPF or DKIM, and senders of around 5,000 messages a day to pass both plus DMARC with an aligned From domain ^S1. To check, send a campaign test to a Gmail address and open the message details. A “mailed-by” and a “signed-by” line showing your domain mean the message is authenticated; a question mark next to the sender’s name means it is not ^S2. For the full result, use Show original, which opens the complete header ^S8.

2. Your sender reputation is weak

Sender reputation is the history a provider keeps for your domain and sending IPs. A new domain has none, and a domain that has sent to poor lists has a bad one. Providers do not publish a score you can look up, so check it indirectly: compare placement of the same test across Gmail, Yahoo and Outlook addresses, and read the delivery errors in your sending tool. A domain that lands in the inbox at one provider and in spam at another usually has a reputation problem rather than a content problem.

3. Recipients are marking you as spam

Complaints are the strongest negative signal. Gmail requires a spam complaint rate below 0.3% and recommends staying below 0.10% ^S1; Yahoo also sets 0.3% ^S6. Check Gmail’s rate in the spam rate dashboard of Google Postmaster Tools, which counts reports on mail delivered to the inbox ^S3. For Yahoo and AOL addresses, Yahoo’s Complaint Feedback Loop sends a report each time a user marks your message as spam; your email provider usually enrolls your domain ^S7.

4. The list includes people who never asked

Google’s guidelines say not to buy addresses and not to email people who did not sign up ^S1. Old addresses cause a quieter version of the same problem: they bounce, or they have been abandoned and later recycled as spam traps. Check by sorting your contacts by source and last engagement. If Ninefold imported a trade-show list or has subscribers who have not opened in a year, those contacts are where to look. A hard bounce should go straight to your suppression list.

5. Content and links look risky

Content matters less than most people assume, but some patterns do hurt. Google asks that links in the body be visible and easy to understand, that HTML and CSS are not used to hide content, and that different kinds of content, such as receipts and promotions, are not mixed in one message ^S1. Check by reading the email as a stranger would: does every link go where its text says, is the sender name your shop’s name, and does the subject match the body?

6. Volume jumped suddenly

Google recommends starting new sending at low volume to engaged recipients, sending at a consistent rate and avoiding sudden spikes without a history of large sends ^S1. A shop that mails 800 people a month and then sends to 12,000 for Black Friday fits that pattern exactly. Check your send log for the last campaign that worked and compare its size with the one that did not. A new domain needs a deliberate warm-up.

7. Unsubscribing is hard or missing

If people cannot leave easily, they press the spam button instead, which feeds cause 3. Gmail and Yahoo require bulk senders to support one-click unsubscribe and a visible link, and Yahoo requires unsubscribes to be honored within two days ^S1S6. Check the raw header of a test for List-Unsubscribe and List-Unsubscribe-Post, and the footer for a link that works in one step. The email footer checker can help with the visible part.

Match the symptom to the cause#

How to test inbox placement honestly#

Sending a test to your own inbox tells you less than it seems. Filters weigh each recipient’s own history with you, so your address, which opens everything you send, is the friendliest audience you have. Use tests to confirm authentication and rendering, and use provider data to judge placement.

• Set up Google Postmaster Tools by adding your sending domain and verifying it with a DNS record ^S4. Data may be missing on days when your Gmail volume is low, so small shops often see gaps ^S4.
• Use the Compliance status dashboard, which marks each Gmail sender requirement as compliant, needs work or no data found ^S3.
• Read the spam rate dashboard after every campaign rather than once a month ^S3.
• Note that the newer version of Postmaster Tools does not carry the old domain and IP reputation dashboards, and the legacy interface is being retired ^S5. Guides that tell you to read a reputation score there are out of date.
• Send seed tests to a few addresses you control at Gmail, Yahoo and Outlook, but treat the result as a hint, not proof.

The provider requirements behind these checks are summarized in Gmail and Yahoo sender requirements.

Diagnosing and fixing it with Tellnod in Claude or ChatGPT#

Tellnod is an MCP connector for writing, previewing and sending email from Claude or ChatGPT. Several causes above are handled before you can send: Tellnod gives you the SPF, DKIM and DMARC records and checks them, adds one-click unsubscribe headers, a visible unsubscribe link and your postal address, removes unsubscribed and bounced contacts from every audience, ramps new accounts up gradually and pauses sending automatically if complaints pass 0.1%.

The parts that remain are judgment calls, and they fit well in a conversation. Ninefold’s owner might type:

• “Check whether ninefold.com is set up correctly for sending.”
• “Build a segment of customers who ordered or clicked in the last 90 days and count it.”
• “Draft a short new-arrivals email for that segment and send me a test.”
• “Compare the last two campaigns: bounces, unsubscribes and clicks.”

You see the real email on desktop and mobile, then a confirmation card with the audience, the exclusions and the send time. The AI can prepare a send but cannot confirm it. Setup takes about a minute on the connect page, and the free plan covers 500 contacts and 2,000 emails a month; see pricing.

FAQ#