Postfix - SMTP Banner


A SMTP banner is the protocol banner of SMTP (ie the response that a client will get when it connects to a SMTP server)


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 ESMTP Postfix

  • The banner text follows the status code ESMTP Postfix

  • where:
    • is the domain/hostname
    • ESMTP indicates that this server talks:
      • where the E means Extension (such as size, chunking, …)
    • Postfix is the name of the SMTP application that:

Postfix Configuration

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