Why your newsletter goes to spam — causes and fixes for the sender
Google’s and Yahoo’s sender guidelines name the causes a sender can fix: an unauthenticated domain, a gmail.com sender, too many spam reports, a hard-to-find unsubscribe and a poor list. Here is each cause in the guidelines’ own words, the fix for it and how to check your own status in Google Postmaster Tools.
When a newsletter starts landing in spam, the first instinct is often to rewrite the message. Google’s sender guidelines, however, are mostly about the sender: whether the message is authenticated, who sent it and whether recipients mark it as spam. This page goes through the causes in the order in which they are worth checking, and every claim is read from Google’s, Yahoo’s or an email tool’s own guidance.
The short answer: a checklist
Go through these before you change the content of the message:
- Domain authenticated with the SPF and DKIM records your tool gives you.
- Your own domain as the sender, not gmail.com or another free address.
- Spam rate below 0.1% in Google Postmaster Tools.
- A visible unsubscribe link in every message, with unsubscribes processed within two days.
- A list you collected yourself: no purchased addresses, bounces removed, inactive subscribers pruned.
- A sender name and subject line that tell the truth about who is sending and what the message contains.
An unauthenticated domain
Authentication is the first thing to check. According to Google’s sender guidelines, messages that are not authenticated may be marked as spam or rejected with error 5.7.26. Everyone sending to Gmail accounts must set up at least SPF or DKIM, and the guidelines advise users of an email service to make sure the service authenticates the domain’s messages with SPF and DKIM. In practice this means the DNS records your tool gives you, added to your domain’s settings once. Google also recommends adding a DMARC record at the same time.
A gmail.com address as the sender
If you send your newsletter through an email tool from the same gmail.com address you use for everything else, it will not work. Google’s sender guidelines prohibit impersonating Gmail in the From header and say Gmail applies a DMARC quarantine policy to these messages. According to MailerLite’s help page, a free email provider’s domain cannot be authenticated either, because you have no access to its DNS records. The fix is your own domain, for example news@yourcompany.com. What it means on free plans is covered in the free email marketing comparison.
Too many recipients mark the message as spam
Once authentication is in order, the most important single figure is the spam rate. Google’s sender guidelines tell senders to keep the rate shown in Postmaster Tools below 0.10% and to avoid ever reaching 0.30% or higher. If 1,000 messages reach the inbox, 0.3% is three spam reports. The limit in Yahoo’s sender best practices is the same 0.3%.
Reports add up. According to Google, if messages from a domain are often marked as spam, future messages are more likely to be marked as spam too, and over time the reports weaken the domain’s reputation. The fix does not show immediately either: according to the guidelines, an improved spam rate may only be reflected in classification after some time.
Unsubscribing is difficult or missing
Unsubscribing and the spam rate are linked. According to the Postmaster Tools help page, the one-click unsubscribe status can show as needing work if recipients mark many messages without one-click unsubscribe as spam. Google advises always giving recipients an easy way to unsubscribe and says that letting people leave can improve open and click rates. Senders of more than 5,000 messages a day to Gmail accounts must also offer one-click unsubscribe. According to the same page, the item is also flagged as needing work if unsubscribes are not processed within 48 hours, and in Yahoo’s guidelines the deadline is two days. The data protection side of unsubscribing is covered in the guide to email marketing and GDPR.
List quality: purchased, bouncing and inactive addresses
According to Google’s sender guidelines, you should only send to people who want your messages, because they are less likely to mark them as spam. The guidelines name three things on the list to fix.
Purchased addresses
Google says it plainly: do not buy email addresses from other companies. According to the guidelines, people who did not sign up for your messages may mark them as spam, and future messages to them will then be marked as spam. All the tools in the table below also prohibit purchased lists in their own terms or guidance.
Bouncing addresses
Google advises automatically unsubscribing recipients whose messages bounce repeatedly. If bounces start to pile up, the guidelines say to reduce sending volume until the errors decrease and then increase it slowly. The same applies to an old list that has not been mailed for a long time: according to Google, suddenly doubling your sending volume can lead to rate limiting or a drop in reputation.
Inactive subscribers
Google’s guidelines recommend periodically sending a message asking subscribers to confirm they want to stay on the list, and considering unsubscribing those who do not open or read your messages. Do not fixate on the open rate, though: Google does not track open rates, and according to Google a low open rate does not necessarily indicate a deliverability or spam problem.
A misleading sender name or subject line
On message content, Google’s sender guidelines are above all about not misleading recipients. A subject line must not start with “Re:” or “Fwd:” unless the message is a real reply or forward, content must not be hidden with HTML and CSS, and the sender name must identify the sender rather than the topic of the message. The guidelines give names such as “URGENT REQUEST” and “Last Chance” as bad examples. Messages of the same type are best sent from the same address, for example newsletters always from a news@ address.
What your email tool does for you
Part of list maintenance happens automatically in the tool, and part is left to you. The table below is read from each tool’s own help pages, and every cell links to the page the information comes from.
| Tool | Bounces and complaints removed automatically | Built-in list cleaning | Deliverability meter in the app | Purchased lists banned |
|---|---|---|---|---|
| Systeme.io | Yes | No | — | Yes |
| EmailOctopus | Yes | No | — | Yes |
| Brevo | Yes | No | Yes | Yes |
| MailerLite | Yes | Yes | — | Yes |
| Mailchimp | Yes | Yes | — | Yes |
| GetResponse | Yes | Yes | — | Yes |
| ActiveCampaign | Yes | Yes | No | Yes |
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Yes = the help page describes the feature. No = the help page says it is absent or points to an external tool. — = not found in the help pages; that does not mean the feature is absent.
In every tool in the table, a hard bounce or a spam complaint stops sending to that recipient automatically, so you do not need to clean up bounces by hand. Pruning inactive subscribers is where they differ. MailerLite has its own tab for cleaning up inactive subscribers, ActiveCampaign’s Engagement Management tool unsubscribes inactive contacts, and Mailchimp’s Omnivore checks imports and sends for risky addresses. Brevo’s help page advises segmenting inactive contacts and blocklisting them by hand. According to the help pages, Brevo, for example, has a deliverability meter in the app. For the other differences between two popular tools, see MailerLite vs Brevo.
How to see where you stand: Google Postmaster Tools
Instead of guessing, you can see your status in Google’s own tool. According to the Postmaster Tools setup guide, you add your sending domain, meaning the DKIM or SPF domain, and verify it by copying a TXT or CNAME record into your DNS settings. The data only covers messages sent to personal Gmail accounts.
The guide to the dashboards explains what to look at:
- Spam rate shows what share of the messages delivered to the inbox recipients marked as spam. It is calculated from DKIM-authenticated messages.
- Compliance status shows whether your sending meets Google’s requirements, such as authentication and spam rate.
- Authentication and delivery errors show what share of messages pass SPF, DKIM and DMARC and what share are rejected or delayed.
Two caveats for a small sender. According to the guide, data may not be shown for every day when sending volume is low, and it is usually updated within 24 hours. A low spam rate can also mislead: if Gmail already routes a large share of your messages to spam, the figure looks small because few messages reach the inbox to be reported.
What to do now
- Authenticate your domain following your tool’s instructions, and switch the sender to your own domain if you send from a gmail.com address.
- Set up Postmaster Tools during the same DNS visit and check the spam rate a week later.
- Check the unsubscribe link in any templates you built yourself.
- Clean the list: remove purchased and inactive addresses, and send to an old list in a smaller batch first.
If you are considering a different tool, the comparison of email marketing software shows prices at three list sizes. According to Google, though, the tool alone will not solve the problem: Google does not accept allowlist requests from email service providers and cannot guarantee that messages sent through a provider will pass Gmail’s spam filters.