SMTP Banner Mismatch Error

SMTP Banner mismatch error when troubleshooting for email delivery issues. The server hostname does not match SMTP Banner according to MXtoolbox.com.  The warning may appear as

The SMTP banner issued by your email server did not contain the hostname we resolved for your server’s IP address.

Related Articles

Outbound Emails Labeled as Spam by Recipient
Update Hostname and PTR

Normalize Hostname and PTR

NOTE: Typically this issue is caused when the server's PTR record and hostname do not match.

1. SSH into the server
2. Run the following command

   echo; echo -e "Hostname:"; hostname; echo -e "PTR:"; dig -x `hostname -i` +short; echo;

3. If the hostname and PTR do not match in the output
   
   1. Confirm the desired hostname
      TIP: It is recommended to use a non-generic hostname such as server.domain.com.
      REPLACE: domain.com with the primary domain.
   2. Reach out to support to have the hostname and PTR record updated
      NOTE: DNS changes can take up to 24 hours to propagate.