If your emails are not reaching Gmail inboxes, whether they are being rejected, delayed, landing in spam, or sorted into the Promotions tab, this article covers the most common causes and how to fix them.
Before you start
- Find your bounce details in Brevo. Bounce details include the error code returned by Gmail's mail server. To learn how to find them, check our dedicated article What is a soft bounce and a hard bounce in email?.
- Set up Google Postmaster Tools. This free Google tool shows your domain reputation, spam rate, and delivery errors at Gmail. It is referenced in several sections of this article. Data is only available from the date you verify your domain. Historical data cannot be retrieved retroactively. To set it up, follow Google's official documentation.
Find the right section
Use the tabs below to navigate to the section that matches your situation.
Use this table to match your symptom to its likely cause and find the right section.
What you are seeing |
Possible cause |
Go to |
|---|---|---|
| Emails rejected, not delivered at all | Domain authentication failure or active block | Domain authentication failure or Active block |
| Emails delayed but eventually delivered | Rate limiting or temporary authentication failure | Delivery delays and rate limiting or Domain authentication failure |
| Emails delivered but going to spam, affecting all campaigns consistently | Sender reputation issues | Emails landing in spam (Sender reputation issues) |
| Emails delivered but going to spam, affecting only specific campaigns | Content filtering | Emails landing in spam (Content filtering) |
| Emails landing in the Promotions tab | Gmail tab classification | Promotions tab placement |
Use this table to match your error code to its likely cause. Some codes are broad and can signal more than one issue. Always read the full bounce message text alongside the code.
Error code |
Possible cause |
Go to |
|---|---|---|
|
Authentication failure: email permanently rejected | Domain authentication failure |
|
Authentication failure: email temporarily rate limited | Domain authentication failure |
|
Unusual rate of unsolicited email detected from your domain or IP | Emails landing in spam (Sender reputation issues) |
550 5.7.1 |
Broad policy rejection: can indicate spam filtering, low reputation, RFC compliance failure, or active block. Read the full bounce message to identify the specific cause. | Active block or Sender reputation issues |
421 4.7.0 |
Broad temporary rejection: can indicate rate limiting, low reputation, or content issues. Read the full bounce message to identify the specific cause. | Delivery delays and rate limiting or Emails landing in spam (Sender reputation issues) |
Domain authentication failure
Domain authentication is how Gmail checks that your email was genuinely sent by you, and not by someone pretending to be you. When domain authentication fails, Gmail rejects the email before it reaches the inbox. It is the most common cause of delivery failures and should always be checked first.
Signs of domain authentication failure
Common signs of domain authentication failure are:
- Bounce error codes indicating that Gmail has permanently rejected the email due to an authentication failure:
550 5.7.26,550 5.7.27,550 5.7.30, or550 5.7.40. - Bounce error codes indicating that Gmail has temporarily rate limited your emails due to an authentication failure:
421 4.7.26,421 4.7.27,421 4.7.30, or421 4.7.40. - Bounce messages that say "does not have authentication information" or "fails to pass authentication checks".
- All or nearly all your Gmail sends are failing, not just one campaign.
Why this happens
- A DKIM, SPF, or DMARC record is missing or incorrectly configured on your domain.
- The domain in your "From" address does not match the domain your DKIM record is set up for.
- You are sending from multiple platforms with conflicting DNS records.
How to check your domain authentication
Use any of the following methods to check your authentication:
Sender Audit is an external tool that checks whether your SPF, DKIM, and DMARC records are correctly configured and displays the results instantly.
- Go to Sender Audit.
- Click Test now.
- Send a test email from your Brevo account to the email address provided. To learn how to send a test email, check our dedicated article Preview and test your email.
- Review the DKIM, DMARC, and SPF results.
- In Gmail, open a delivered email sent from your Brevo account.
- Click the three-dot menu icon and select Show original.
- Find the ARC-Authentication-Results header.
- Confirm that you see dkim=pass, spf=pass, and dmarc=pass.
How to fix domain authentication issues
➡️ To learn how to fix domain authentication issues, check our dedicated article Troubleshooting - Domain authentication.
Emails landing in spam
If your emails are being delivered but landing in Gmail's spam folder, the cause is either your sender reputation or the content of a specific campaign. Select the tab that matches your situation.
Gmail tracks how recipients respond to your emails over time and analyzes a range of signals, including spam complaints, engagement levels, content, and spam-trap hits. If too many negative signals accumulate, Gmail starts routing all your emails to the spam folder, even for recipients who have never complained. If spam placement is consistent across all your campaigns, sender reputation is the most likely cause.
Signs of sender reputation issues
Common signs of sender reputation issues are:
- Emails are going to spam for most Gmail recipients, across all or most of your campaigns.
- A sudden drop in open rates from Gmail contacts, while other email providers are unaffected.
- Google Postmaster Tools shows your Domain Reputation as Low or Bad.
- Gmail is detecting an unusual rate of unsolicited mail from your domain. You may see error codes
550 5.7.28or421 4.7.28.
Why this happens
- Your complaint rate has exceeded Gmail's thresholds.
- You are sending to old, unengaged, or purchased contact lists.
- A sudden large volume send was made without gradual ramp-up.
- A history of sending to invalid addresses has generated a high bounce rate.
How to check your domain reputation
Open Google Postmaster Tools and review the following panels:
- Domain Reputation: shows Gmail's overall view of your domain: High (green), Medium (yellow), Low (orange), or Bad (red). A drop from High or Medium indicates a recent sending issue.
-
Spam Rate: shows the percentage of recipients who marked your email as spam each day. The following table shows what happens at each level:
Spam rate Status Impact Below 0.08%* Healthy No impact on delivery. 0.08% to 0.10% Warning zone Increased risk of spam placement. Investigate your recent campaigns immediately. Above 0.10% Critical Gmail starts routing more of your emails to spam. Above 0.30% Blocking risk Gmail may actively block your emails. Immediate action is required. 💡 Good to know*Gmail's official thresholds are 0.10% (critical) and 0.30% (blocking risk). Staying below 0.08% is a recommended safety buffer, not an official Google figure.To identify the cause, look for spike dates and match them to specific campaigns in your Brevo account.
- Delivery Errors: shows which error codes Gmail returned and when they occurred.
How to recover from sender reputation issues
Reputation recovery cannot be rushed. The only way to rebuild trust with Gmail is to send consistently to engaged contacts over time. In most cases, expect to see improvement in Google Postmaster Tools after 4 to 6 weeks of following best practices, though this may take longer depending on the severity of the damage.
- Reduce your sending volume immediately to 10 to 20% of your usual volume.
- Send only to Gmail contacts who have opened or clicked one of your emails in the last 30 to 60 days. These are your most engaged contacts and the least likely to mark your emails as spam.
- Move all Gmail contacts who have not engaged in the last 90 days to a separate list. Do not send to them until Google Postmaster Tools shows that your Domain Reputation has improved.
- Maintain this low-volume, high-engagement pattern consistently for at least 30 days.
- Once Domain Reputation improves in Google Postmaster Tools, gradually increase your volume by no more than 20 to 25% per week.
- Ask engaged subscribers to open any of your emails that landed in their spam folder and mark them as Not spam. You can include a short note in your next email to your most engaged contacts, asking them to check their spam folder and click Not spam if they find your emails there. Each action sends a positive signal to Gmail and helps rebuild your domain's reputation.
➡️ For more guidance on rebuilding your sender reputation, check our dedicated article Best practices for email deliverability.
Sometimes the problem is not your domain's overall reputation, but the content of a specific campaign. Gmail filters can flag individual emails for spam-like content, even if your other campaigns deliver normally. If only some campaigns are landing in spam, content filtering is the most likely cause.
Signs of content filtering
Common signs of content filtering are:
- Some campaigns land in Gmail spam, while others from the same sender do not.
- The issue is not consistent across all your sends.
- A Spam Rate spike in Google Postmaster Tools on a specific send date that you can match to a campaign.
Why this happens
- URL shorteners (such as bit.ly) in the email body. These are heavily associated with spam.
- Overly promotional language: excessive use of "FREE", "Act now", "Limited offer", or "Click here".
- Misleading subject lines or "From" names that do not match the email content.
- Emails made up mostly of images with little readable text. These score poorly with Gmail's filters.
- A missing or non-functional List-Unsubscribe header.
What to do to avoid content filtering
- Remove URL shorteners from your emails and replace them with full, branded links.
- Review your subject lines and "From" name. They need to accurately describe the content of the email.
- Balance the image-to-text ratio in your emails. Avoid emails made up mostly of images with very little readable text.
- Reduce overly promotional language. Excessive use of words like "FREE", "Act now", or "Click here" increases your spam score.
Active block
If Gmail is outright rejecting your emails, your domain or IP address has been actively blocked. Unlike spam placement, blocked emails are rejected before they reach the recipient and generate a bounce error.
Signs of an active block
- Bounce error
550 5.7.1on most or all of your sends. Note that this is a broad policy rejection code used by Gmail for many different reasons, including spam filtering, low reputation, and RFC compliance failures. Always read the full bounce message text to identify the specific cause. - Emails are not being delivered at all, not just going to spam.
Why this happens
- Your complaint rate has exceeded Gmail's blocking threshold (above 0.30%).
- Your domain or IP has been listed on a spam blocklist referenced by Gmail. The error message typically specifies which one is affected.
How to fix an active block
➡️ To fix an active block, check our dedicated article FAQs - Why is my IP address or domain blocklisted?.
Delivery delays and rate limiting
If you send a large number of emails too quickly, Gmail temporarily delays delivery. These are temporary holds, not permanent blocks. Gmail retries the emails automatically, so there is no need to resend them manually.
Signs of rate limiting
Common signs of rate limiting are:
- Delivery delays after a large send. You may see error code
421 4.7.0. Note that this is a broad temporary rejection code also used by Gmail for reputation and content issues. Check the full bounce message text to confirm that volume is the cause. - A sudden increase in bounce rate after a large send.
- The issue affects Gmail contacts but not recipients on other email providers in the same send.
Why this happens
- You sent a significantly larger volume than in previous days without warming up gradually.
- You sent a very large list segment all at once rather than spreading it over time.
- You are using a new IP or domain with no established sending history.
What to do to avoid rate limiting
- Spread large sends across multiple hours or days rather than sending everything at once.
- If you are using a new dedicated IP, make sure to warm it up first. To learn more, check our dedicated article Warm up your dedicated IP (manual warm-up) or Warm up your dedicated IP (automatic warm-up).
- If you are using a new domain with no sending history, start small (a few hundred emails per day) and double the volume each week.
Promotions tab placement
If recipients tell you that your emails are landing in the Promotions tab rather than their Primary inbox, this is not a deliverability problem. Emails in the Promotions tab are successfully delivered and can be read normally.
Plain-text or low-design emails are less likely to be placed in the Promotions tab. High engagement signals, such as replies and forwards, also help Gmail learn to categorize your future emails differently.
➡️ To learn more, check our dedicated article Why do emails get delivered to Gmail's Promotions tab.
Diagnostic tools
The following tools can help you diagnose and monitor Gmail deliverability:
Tool |
URL |
What you can do |
|---|---|---|
| Google Postmaster Tools | postmaster.google.com | Monitor domain reputation, spam complaint rate, authentication pass rates, and delivery errors. Requires domain verification. |
| Sender Audit | senderaudit.com | Send a test email to verify that SPF, DKIM, and DMARC are correctly configured. |
| Gmail "Show original" | In Gmail, click the three-dot menu icon and select Show original. | View the raw message headers to confirm authentication results. |
What's next?
- Comply with Gmail, Yahoo, and Microsoft's requirements for email senders
- Troubleshooting - Domain authentication
- FAQs - Why is my IP address or domain blocklisted?
- Best practices for email deliverability
- Best practices for managing a dedicated IP
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