The reason for that metaphor: When email is transported via SMTP, most MTAs examine only the information that’s on the envelope and only a very, very small percentage of MTAs will actually open that envelope and examine the Email Headers and Email Body. A postal worker will most probably examine the sender address as written on the envelope and send the letter back to that address, unless he belongs to that small percentage of really curious postal workers, who will actually unseal your envelope, examine your letter and send it back to the address specified on the letterhead instead. However, imagine the recipient address isn’t valid. Very similar to a postal truck delivering a letter to another postal office, the SMTP server relays your email to other SMTP servers until the message reaches its final recipient. Just like in paper mail – the letterhead and letter body (Email Headers and Email Body) are sealed inside the envelope, while the sender and recipient addresses (MAIL FROM and RCPT TO) are stamped on the envelope. The From and To addresses, as well as the Subject line are also part of the Email Headers – it’s like a letterhead being added to a letter written on paper.Īfter that your email client connects to your outgoing SMTP server and sends it:įrom there on, the SMTP server uses this data to construct an envelope. The Return-Path is the email header responsible for specifying the bounce address according to RFC 2822. These additional fields are called Email Headers. When you compose an email in your email client and click "Send", what the email client does for you is to add some additional information to your message like "Date" and "Return-Path". To understand why Interspire Email Marketer does that, you must first understand how sending emails over the Internet really works. Why does Interspire Email Marketer use my Bounce Address instead of my From Address for sending emails?