In this article we explain the difference between these two addresses in non-technical terms.
The design of a modern e-mail system is based on postal mail.
Therefore, in order to understand how email works, we will analyze how postal mail works.
There are two parts to any package you receive from your regular postal mail: an envelope and a letter inside that envelope.
First part - The envelope (visible by SMTP servers)
It contains the following information:Sender's name and address - (tag 1) in the image. If a package cannot be delivered, the post office will use this address to return it to the sender.
- Name and address of recipients - (tag 2) in the image
- A postage stamp - (tag 3) in the picture
- This letter seems to have been sent by Dupont Marcel who works for Société, X.
Part 2 - Real letter (which presents itself for an email client)
This one contains the following information:- A header up - tag 1 in the image.
- This header contains the sender's information (tag 2) and possibly a date when the letter was composed. (tag 3)
- Real body, which appears at the bottom
Important points to remember:
- Note that the sender's name on the actual letter is BANQUE CIC, which is different from what was specified on the envelope
- If Melinada had not looked at the envelope, she would have thought that the letter was sent by Mr. Gerard who also works for BANQUE CIC. the same company for which Melinda works.
- The sender could easily have put an invalid date and his contact information to try to make her believe that Gerard Lami was the sender
- If Melinda is not careful and does not detect any fraud, she may take actions that should not have been taken otherwise.
- Note that the sender's name on the actual letter is BANQUE CIC, which is different from what was specified on the envelope
- If Melinada had not looked at the envelope, she would have thought that the letter was sent by Mr. Gerard who also works for BANQUE CIC. the same company for which Melinda works.
- The sender could easily have put an invalid date and his contact information to try to make her believe that Gerard Lami was the sender
- If Melinda is not careful and does not detect any fraud, she may take actions that should not have been taken otherwise.