What is a bounced email

A bounced email ( simply a bounce ) is a email message from mail server (MTA) informing the sender of another message about a delivery error. It is also called as a returned mail, an error email, and an undelivered mail. More information about bounced email is described in en.wikipedia.org/wiki/Bounced_e-mail .

Subject: header

A bounced email is created by MTA ( Such as Sendmail, Postfix, and qmail ) automatically when delivery error occurred. Contents of the subject header of bounced email like followings.

• Returned mail: see transcript for details
• Mail System Error - Returned Mail
• Non Delivery Notification
• DELIVERY FAILURE: ...
• Undelivered Mail Returned to Sender
• Postmaster notify: see transcript for details
• Delivery Status Notification (Failure)
• Warning: could not send message for past 4 hour
• failure notice

From: header

A sender of bounced email is mainly postmaster or MAILER-DAEMON. You will find names like the followings in From: header of bounced email.

• MAILER-DAEMON
• MAILER-DAEMON@hostname of mail server
• Postmaster
• Postmaster@hostname of mail server
• Mail Delivery Subsystem
• Mail Delivery System
• Mail Administrator

Message body

A bounced email is created by mail server program such Sendmail, and contains delivery report in its message body.

bounceHammer reads a bounced email and parse its headers and its message body, then find details about why the delivery failed. The following section is particularly important to find details for bounceHammer.

• Status: 5.1.1 <- Various error codes
• Diagnostic-Code: ... <- Error message, response of SMTP server, and so on.

bounceHammer is a system which parses a bounced email, finds a reason of bounce, classifies a recipient (PC, Webmail, smartphone ). Visit What is bounceHammer ? page to read more information about bounceHammer.