How to Fix ‘Message Blocked: Your Message Was Blocked by Gmail’ Error

Sending an important email only to receive an immediate bounce-back notification from Mail Delivery Subsystem declaring “Message blocked: Your message to [recipient] has been blocked. See technical details below for more information”, accompanied by SMTP error codes such as 550-5.7.1 or 550 5.7.26, is a disruptive communication barrier. Gmail enforces automated inbound spam filtering, domain authentication verifications, and machine learning heuristics across all incoming and outgoing messages. When an email contains suspicious tracking URLs, lacks cryptographic sender validation, triggers attachment signature blocks, or originates from an IP address with a degraded reputation, Google’s SMTP transfer agents reject the transmission. This guide outlines how to decode Gmail’s bounce headers, configure essential email authentication records, and restore deliverability.

Underlying Triggers for Gmail ‘Message Blocked’ Errors

Gmail’s inbound mail servers scrutinise every incoming message before delivering it to a recipient’s inbox. The most frequent causes of hard bounces include:

• Missing or Failing SPF, DKIM, and DMARC Records: Google requires bulk and corporate senders to implement strict cryptographic authentication. Emails originating from domains without matching Sender Policy Framework (SPF) or DomainKeys Identified Mail (DKIM) signatures are rejected outright.
• Blocked Attachment File Extensions: Gmail permanently blocks messages containing executable files or scripts (such as .exe, .bat, .vbs, .cmd, and password-protected archives containing scripts), even inside ZIP or RAR files.
• Shortened or Flagged Hyperlinks: Using URL shorteners (like bit.ly) or linking to newly registered domains that Google Safe Browsing has flagged for phishing or malware distribution.
• Sending Quota Exceeded: Personal Gmail accounts are limited to 500 recipients per 24 hours, while Google Workspace accounts allow 2,000 recipients. Exceeding these thresholds triggers automated 24-hour transmission lockouts.
• High Recipient Spam Complaint Rates: If more than 0.3% of your recipients mark your previous messages as spam, Google’s filters automatically drop subsequent communications.

Method 1: Verify and Configure SPF, DKIM, and DMARC DNS Records

If sending from a custom domain (e.g. [email protected]), valid authentication records are mandatory for Gmail delivery.

1. Log in to your domain name registrar or DNS management portal (Cloudflare, GoDaddy, Namecheap, etc.).
2. Verify your SPF TXT Record: Ensure your DNS contains a TXT record for @ containing v=spf1 include:_spf.google.com ~all (or including your specific email host).
3. Verify your DKIM TXT Record: In your Google Workspace Admin console, navigate to Apps > Google Workspace > Gmail > Authenticate email, generate a 2048-bit DKIM key, and publish the resulting TXT record to your DNS host.
4. Verify your DMARC Record: Add a TXT record for _dmarc.yourdomain.com with at least a monitoring policy:

   v=DMARC1; p=none; rua=mailto:[email protected];

5. Use an email validator tool (such as Google Postmaster Tools or MXToolbox) to confirm that all three records resolve cleanly without syntax errors.

Method 2: Remove Blocked Attachments and Use Cloud Sharing

Gmail’s security gateway inspects the binary headers of all attachments, detecting disguised scripts and compressed executables.

1. Inspect your bounced message for attachments ending in .exe, .dll, .iso, .js, or .vbs.
2. Remove the attachment from the email draft.
3. Upload the file to Google Drive, OneDrive, or Dropbox.
4. Set the file sharing permissions to “Anyone with the link can view” (or restrict it to specific recipient addresses).
5. Paste the secure cloud link into the body of your email and resend the message.

Method 3: Remove Suspicious Links and URL Shorteners

Spam filters heavily penalise emails containing generic link shorteners that obscure the final destination URL.

1. Review the body text and HTML signature of your email.
2. Replace all shortened URLs with full, direct, and transparent URLs using standard HTTPS protocols.
3. Ensure that your email signature does not contain links to social media profiles or websites hosted on free dynamic DNS hosts.
4. Ensure your text-to-link ratio remains balanced; single-image emails containing only a hyperlink are classified as spam by automated heuristic scanners.

Method 4: Check Domain Reputation via Google Postmaster Tools

If you manage bulk business emails and continue experiencing delivery blocks, Postmaster Tools reveals your domain’s health score.

1. Navigate to postmaster.google.com.
2. Click the + button to add and verify your sending domain via a DNS TXT verification token.
3. Review the Domain Reputation and IP Reputation dashboards. If your reputation is classified as “Low” or “Bad”, temporarily pause marketing campaigns, clean your mailing lists of unengaged subscribers, and focus on transactional emails until your score recovers to “High”.