Envelope sender

As Envelope transmitter ( English for, envelope stations') or " sender " is the e-mail address designated during an SMTP -Handshakes according to RFC 5321 as a parameter of MAIL FROM: is passed.

The designation Envelope (English for 'envelope', 'shell') is based on the envelope. As with letter post, only what is written on the envelope is decisive for transport. The envelope sender corresponds to the sender, the envelope To the recipient. As with letter post, the sender is informed on the envelope (envelope sender) if his message could not be delivered - regardless of which sender is named in the message itself ( Body From: Header ). Bounce reply messages ( bounce messages ) are with an empty sender Envelope ( <>) sent to e-mail loops to prevent.

If the e-mail is saved in mbox format, the envelope sender is contained in the first line of the e-mail.

For example, if a mail is sent with the following SMTP commands:

MAIL FROM:<[email protected]>
RCPT TO:<[email protected]>

this creates the following line in front of the header of the received email:

Envelope-From [email protected] Wed Jun 22 13:49:30 2005

The field can also have other names depending on the servers involved, e.g. B. Return-Path or X-Envelope-From. The envelope sender is normally not displayed by e-mail programs , but can be made visible using special functions (e.g. show header, show raw, show message source text, properties ...). As with a letter, you can also give the wrong sender, so you should never rely on this information. You can only rely on Envelope-To as long as your own mail server has not been manipulated, because if Envelope-To had been manipulated beforehand, the email would not have arrived.

The domain part of the envelope sender can be checked with SPF . Many e-mail providers do this automatically and write the result under the name Received-SPFin the header, which can be viewed as stated above.

Web links

• RFC 5321 - Simple Mail Transfer Protocol