SMTP Banner
Also known as: Service banner
The SMTP banner is the initial text greeting a mail server sends when a connection is first established.
An SMTP banner is the "hello" message a mail server (MTA) sends immediately after a connection is made, before any email data is transferred. It usually contains the server's hostname and the software it is running (e.g., 220 mail.example.com ESMTP Postfix).
This banner is important for troubleshooting and reputation. Many anti-spam systems perform a "banner check" to ensure the hostname in the banner matches the Reverse DNS (PTR) record of the IP address connecting. If they don't match, the connection might be penalized or dropped.
It is best practice to configure your SMTP banner to display your fully qualified domain name (FQDN).
Related Terms
SMTP
SMTP (Simple Mail Transfer Protocol) is the standard way email servers send messages to each other. It handles the handoff from your email tool to the recipient's mail server so messages can land in the inbox.
Learn more →Alternative Text(Alt Text)
Short text that explains what an image shows and why it is in your email. It helps people and email clients understand your message when the image does not load.
Learn more →Mail Loop(Routing loop)
A mail loop occurs when an email is forwarded back and forth between servers without ever reaching a final destination.
Learn more →Backscatter(Blowback)
Backscatter is when a mail server sends bounce messages to an innocent third party because their email address was spoofed by a spammer.
Learn more →