About
A SMTP banner is the protocol banner of SMTP (ie the response that a client will get when it connects to a SMTP server)
Example
With Telnet, we connect to the local smtp server submission port
nc localhost 25
- We receive an SMTP greeting where 220 is a reply code that means all is good (an equivalent to the 200 HTTP status code)
220 server01.bytle.net ESMTP Postfix
- The banner text follows the status code
server01.bytle.net ESMTP Postfix
- where:
- server01.bytle.net is the domain/hostname
- ESMTP indicates that this server talks:
- the SMTP protocol
- where the E means Extension (such as size, chunking, …)
- Postfix is the name of the SMTP application that:
- has implemented the SMTP protocol
- replies.
Postfix Configuration
- postconf.5.html it default to $myhostname ESMTP $mail_name