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Introduction

This guide addresses the issue of emails being blocked by Gmail and outlines steps for administrators to prevent such blocks in the future. Gmail often blocks emails from servers that do not meet its stringent security and spam-prevention measures. This issue primarily affects businesses or individuals sending emails via their own mail servers, where incorrect configurations or a poor sending reputation may lead to blacklisting. The solution includes reviewing and adjusting key configurations such as SPF, DKIM, and DMARC records, checking IP blacklists, and ensuring proper server setup to improve email deliverability.

Prerequisites

Before proceeding, ensure you have access to:

• Your domain’s DNS management panel.
• Access to email logs for diagnostic purposes.

Issue/Error Message Received:

When sending an email to Gmail, it returns a bounced-back error similar to the one below:

This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: sample@gmail.com SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com [2607:f8b0:400e:c02::1b]: 550-5.7.1 [2002:d205:2c22:a:20c:29ff:fe7c:43a4 12] Our system has detected 550-5.7.1 that this message is likely unsolicited mail. To reduce the amount of 550-5.7.1 spam sent to Gmail, this message has been blocked. Please visit 550-5.7.1 http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for 550 5.7.1 more information.

Reason:

Gmail may classify a message as spam and deliver it to the spam folder. Gmail also tries to reduce the amount of spam being sent. If a message has a high likelihood of being spam, it might get blocked. This can happen if the message contains suspicious text or if the sending IP has a history of sending unsolicited messages.

Step-by-step guide

1. Verify SPF (Sender Policy Framework) record

• • Gmail requires an SPF record to verify that the server sending an email on behalf of your domain is authorized to do so.
  • To check if your SPF record is set up correctly:
    • Go to your DNS management panel.
    • Ensure that your SPF record includes your sending mail server’s IP address. An example of a correct SPF record is:

      v=spf1 a mx ip4:your_server_ip ~all
  • You can also use MXToolbox SPF checker to validate your SPF record.

2. Set up DKIM (DomainKeys Identified Mail)

• • DKIM adds a digital signature to the email headers, allowing the receiving server to verify that the email hasn’t been altered during transmission.
    • Access your DNS settings and generate a DKIM key from your mail server.
    • Add the public key to your domain’s DNS as a TXT record.
    • Enable DKIM signing in your mail server’s email settings.
  • Test the DKIM setup using MXToolbox DKIM checker to ensure everything is properly configured.

3. Implement DMARC (Domain-based Message Authentication, Reporting, and Conformance)

• • DMARC policies help mail servers decide how to handle emails that fail SPF or DKIM checks.
    • In your DNS management panel, create a DMARC record as a TXT entry. A typical DMARC record looks like this:

      v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com

    • Once set up, this will provide reports on how your domain’s emails are being treated by recipients.

4. Check if your IP is blacklisted

• • If Gmail has blocked your emails, your mail server’s IP address may be blacklisted. Use tools like MXToolbox Blacklist Checker to check if your IP address is on a blacklist.
  • If your IP is blacklisted, follow the specific blacklist’s delisting procedure. This may involve fixing spam issues or securing your server to prevent abuse.

5. Review email sending practices

• • To improve email deliverability, ensure you are following these best practices:
    1. Avoid sending emails in bulk or with misleading subject lines.
    2. Ensure your emails contain both text and HTML components.
    3. Regularly monitor your server logs to detect and address any suspicious activities.
    4. Encourage recipients to mark your emails as “Not Spam” to improve your sending reputation.

Optional: Contact Gmail support

• • If none of the above steps resolve the issue, contact Gmail support by visiting the Google Postmaster Tools site. Set up an account and provide the required information to get insights into your domain’s email reputation and troubleshoot delivery issues.

Conclusion

Email blocking by Gmail can be frustrating, but by ensuring that your domain is properly configured with DKIM and SPF records, and by adhering to Google’s Bulk Senders Guidelines, you can significantly reduce the chances of your emails being flagged as spam. By configuring SPF, DKIM, and DMARC records and ensuring your server’s IP is not blacklisted, you can improve your email deliverability and prevent emails from being blocked by Gmail. Following best practices for sending emails and monitoring your server logs can further protect your email system from being blacklisted.

For additional assistance or if you encounter any issues, please contact our support team at support@ipserverone.com.

Article posted on 8 April 2020 by IPSERVERONE