How to Fix Reverse DNS does not match the SMTP banner Error

The “reverse DNS does not match SMTP banner” error occurs when the domain name in your mail server’s greeting message doesn’t match its reverse DNS (PTR) record. This mismatch affects email authentication, often leading to deliverability issues or rejections by providers like Gmail or Outlook. 

The reverse DNS ensures your IP correctly maps to your domain, while the SMTP banner identifies your mail server during an email transaction. If these two records don’t align, receiving mail servers suspect spoofing or poor configuration. 

Understanding and fixing this issue helps ensure your emails pass verification checks, maintain sender reputation, and reach inboxes reliably without unnecessary filtering or blocking.

What is Reverse DNS?

Reverse DNS (rDNS) is a process that maps an IP address back to its associated domain name. This is basically the opposite of a regular DNS lookup. When a mail server receives an email, it checks if the sending IP’s reverse DNS record points back to the same domain mentioned in the SMTP banner. If it doesn’t, you’ll likely face errors like “reverse DNS does not match SMTP banner.”

For better understanding, think of it like caller ID; if the name and number don’t align, the receiver gets suspicious.

What is an SMTP Banner?

An SMTP banner is the first message your mail server sends when it connects to another mail server to send an email. It shows the name of your mail server, usually something like “mail.yourdomain.com.” This helps the receiving server identify who the email is coming from. 

The SMTP banner is part of the process that mail servers use to communicate with each other and verify the authenticity of senders. If the name in your SMTP banner does not match your reverse DNS or domain name, other servers may think your setup is wrong or unsafe and might reject your emails.

Why Should Reverse DNS and SMTP Banner Must Match

Making sure your reverse DNS and SMTP banner match helps mail servers trust your emails. Platforms like Gmail, Microsoft, and Yahoo check this match to verify your domain’s identity. If the reverse DNS does not match the SMTP banner, your emails might look suspicious and could get rejected.

For example, the “Gmail reverse DNS does not match SMTP banner” error usually prompts when Google finds a mismatch between your server’s hostname and its reverse DNS record. It’s one of the most common reasons behind email delivery issues.

Reasons Why Reverse DNS Does Not Match the SMTP Banner

The issue usually happens due to simple but critical configuration errors. Here are the main technical reasons that lead to this problem:

1. Misconfigured DNS Records

A mismatch often occurs because the DNS records are not properly aligned with the mail server hostname. The PTR (reverse DNS) record may point to a different domain, or the A record may not resolve to the same IP. This confusion often causes delivery issues, such as “Gmail reverse DNS does not match SMTP banner” or “reverse DNS does not match SMTP banner Google Workspace.”

2. Incorrect SMTP Server Settings

If the SMTP banner presents a hostname that doesn’t match the reverse DNS record, mail servers treat it as untrustworthy. This usually happens when administrators forget to update the HELO or EHLO hostname after changing domains or migrating servers. 

3.Hosting Multiple Domains on a Single IP

In shared hosting environments, multiple domains may share one IP address, which can lead to the issue. Because each IP address can have only one PTR record, a domain’s reverse DNS may conflict with another’s SMTP banner. This is common in cPanel reverse DNS does not match SMTP banner cases.

How to Fix the “Reverse DNS Does Not Match SMTP Banner” Issue

Fixing the “reverse DNS does not match SMTP banner” error involves checking both DNS and server configurations to make sure they point to the same domain name. Follow these five steps to identify and fix the mismatch effectively.

1. Diagnosis: How to Identify the Reverse DNS and SMTP Mismatch

Use online tools to see what your mail server announces in its SMTP banner. If this banner doesn’t match the domain shown in your reverse DNS record, it confirms that the “reverse DNS does not match SMTP banner” problem exists.

Also, review the headers of bounced or delayed emails. They often contain details about hostname mismatches or DNS issues. Look for warnings such as “Gmail reverse DNS does not match SMTP banner” to identify where the inconsistency lies.

2. DNS Configuration: How to Correct Reverse DNS Records

Go to your DNS or hosting panel and verify the PTR record for your server’s IP address. The reverse DNS should map cleanly to the same hostname used in your SMTP banner. If not, you’ll likely face errors such as “reverse DNS does not match SMTP banner Google Workspace.”

Then, you need to confirm that the A record for your mail hostname resolves to the same IP linked with the PTR record. Both forward and reverse lookups must match perfectly for smooth verification and to avoid mail rejection.

3. SMTP Server Settings: How to Adjust Your Mail Server Configuration

Log in to your mail server settings and check what hostname appears in the greeting line when you use diagnostic tools. If you notice the hostname differs from your PTR entry, especially in “cPanel reverse DNS does not match SMTP banner” cases, update it immediately.

Update your SMTP banner so that it shows the exact same hostname listed in your PTR and A records. For instance, if your PTR record resolves to mail.domain.com, the SMTP banner should also identify as mail.domain.com. Adjust this according to your mail software.

4. Verification: How to Confirm Your Fix Worked

After updating DNS and SMTP settings, send test messages to providers like Gmail, Outlook, and Yahoo. Check that the reverse DNS does not match SMTP banner warning no longer appears in delivery reports.

Then, re-run diagnostic tools like the DNS record lookup to confirm that your SMTP banner and reverse DNS records match.

5. Validation: How to Double-Check Server and Header Alignment

Finally, send a test email to yourself and inspect its full headers. Ensure there are no signs of “reverse DNS does not match SMTP banner” or related warnings. A clean header confirms your configuration is properly aligned and your email authentication is functioning correctly.

Final Thoughts

The “reverse DNS does not match SMTP banner” issue may seem minor, but it can severely impact how mail providers evaluate your emails. Aligning the PTR record, A record, and SMTP banner ensures your domain’s identity is verified correctly during every mail exchange. 

Once your server settings and DNS entries match, delivery errors like “Gmail reverse DNS does not match SMTP banner” or “cPanel reverse DNS does not match SMTP banner” will disappear. 

We recommend using the DNS record lookup tool to confirm everything’s aligned. A well-configured DNS setup not only boosts deliverability but also strengthens your domain’s trust and compliance with modern email authentication standards.

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