Why your newsletter is going to spam (and how to fix it)

If your newsletter is landing in spam folders, the cause is almost never the words in the email. It is usually a combination of authentication, list hygiene, and sender reputation. Fixing it is mostly a checklist exercise.

Here is the short version, in priority order.

Authentication is the first thing to check

If your domain is not properly authenticated, mailbox providers will treat your sends as suspicious by default. Three records do most of the work.

SPF (Sender Policy Framework) tells receiving servers which IP addresses are allowed to send email on behalf of your domain. Most ESPs (Mailchimp, Beehiiv, Klaviyo, Resend, ConvertKit) provide an SPF record to add to your DNS during setup. If you skipped this step, do it now.

DKIM (DomainKeys Identified Mail) signs your messages with a cryptographic key that proves the email actually came from you and was not modified in transit. Same story: your ESP gives you a DKIM record, you add it to DNS.

DMARC (Domain-based Message Authentication) tells receiving servers what to do if SPF or DKIM fails. As of February 2024, both Google and Yahoo started requiring DMARC for any sender who emails more than 5,000 messages per day to their respective domains. The bar has been quietly raised for everyone, and unauthenticated senders are getting filtered more aggressively.

Set DMARC to at least p=none to start, which lets you collect reports without affecting delivery. Move to p=quarantine once you have confirmed your authentication is clean.

Check your records at mxtoolbox.com or mailauth.report. If any of the three are missing, your spam problem starts there.

List hygiene is the second thing to check

Mailbox providers track engagement. If you keep emailing addresses that never open, never click, or that bounce, your sender reputation drops and the people who do want to read you start landing in spam too.

Three rules.

Remove hard bounces immediately. Most ESPs do this automatically, but check the setting. Continuing to send to invalid addresses is a fast way to tank deliverability.

Suppress addresses that have not engaged in ninety days. Send them a re-engagement sequence first. If they do not respond, suppress. The discomfort of "shrinking the list" is real, but it improves delivery for everyone who remains.

Never send to lists you bought, scraped, or added without consent. The deliverability damage is severe and the conversion is essentially zero. Unless the recipients explicitly opted in to your specific newsletter, you are gambling with the rest of your list.

The cleanest lists come from double opt-in (where subscribers confirm via a link before being added). Single opt-in works fine if your acquisition channels are clean, but double opt-in is the safer default for higher-volume senders.

Content patterns that look spammy

These matter less than authentication and engagement, but they still move the needle.

Subject lines in all caps. Even if you are not screaming, the filter thinks you are.

Excessive exclamation marks. Anything more than one is a flag. Anything more than two reads as desperate to a reader and as spam to a filter.

Spam-trigger words used carelessly. "Free," "guarantee," "amazing offer," "act now," "limited time" used in combination, especially in subject lines, push spam scores up. Used naturally in body copy with normal context, they are fine. Used in marketing-speak stack-ups, they are not.

Heavy image-to-text ratio. Emails that are mostly images with very little text get filtered as suspicious. Aim for at least sixty percent text by visual weight. Always include alt text for images.

Single giant image with no text. The classic spam pattern, because it bypasses text-based filters. Avoid.

Suspicious links. URLs that have been recently registered, that point to free hosting, or that hide the destination behind URL shorteners get flagged. Use links to your own well-established domains where possible.

Sender reputation matters more than content

Mailbox providers maintain reputation scores for sending domains and IP addresses. Reputation is built over months and lost in days.

If you send a single bad campaign (cold list, high bounce rate, lots of unsubscribes), your reputation can drop materially for weeks. The fix is not to send more aggressively to make up for it. The fix is to send less, to your most engaged subscribers only, until reputation recovers.

Tools like Google Postmaster Tools (free, requires DNS verification) show you exactly how Gmail rates your domain. Microsoft offers SNDS for similar visibility into Outlook. If your spam complaint rate is above 0.3 percent or your domain reputation drops to "low," you have a problem and should pause until you understand why.

The Apple Mail privacy effect

Since Apple Mail Privacy Protection rolled out in 2021, open rates have become much less reliable as a metric. Apple pre-fetches email content for many users, which inflates apparent opens whether or not the user actually opened the email.

This matters for spam reasons because some senders chase higher open rates by sending to inflated lists, which then performs worse on the metrics that filters actually use (clicks, replies, manual deletions, "this is spam" reports).

The fix is to optimise for engagement metrics that are real: clicks, replies, scrolls, and pages visited. Open rate is now noise above signal in most consumer-facing newsletters.

What to do if you are already in spam

Order of operations matters. Do the cheap things first.

First, fix authentication. SPF, DKIM, DMARC. Verify with a tool. This alone often clears up the problem within a week.

Second, prune the list. Suppress everyone who has not opened or clicked in ninety days. Yes, the list will shrink. Yes, you will feel anxious about it. The remaining list will perform dramatically better.

Third, send to engaged subscribers only for thirty days. No promotional pushes, no cold outreach, just normal content to your warmest segment. This rebuilds reputation.

Fourth, fix the content patterns. Reduce subject-line all-caps, drop the worst spam-trigger words, fix image-to-text ratios.

Fifth, if you are still in spam after thirty days, consider warming a new subdomain. Some ESPs let you migrate to news.yourdomain.com and warm it up gradually. This is heavier surgery and you should not need it for most senders, but it is an option.

Test before you send

Two free tools tell you what mailbox providers will do with your email before you send it.

mail-tester.com gives you a 0-10 score for any email you send to their address. It checks authentication, content patterns, and link reputation. Aim for 9 or 10 before sending to your real list.

gmass.co/spam-test shows where your email lands in Gmail and Outlook seed inboxes. Useful for catching domain-specific filtering.

Run these for the first edition of any new newsletter, after any major change to your sender setup, and quarterly for ongoing health checks.

The honest reality

Most spam-folder problems clear up within two weeks of a clean checklist run. The senders who stay in spam for months tend to share a common pattern: they bought a list, never authenticated, and assumed it was a content problem. It is almost always not.

For more on the technical side of email infrastructure, see email deliverability basics for newsletter creators.

Cheers.