What is the difference between mail from in smtp and from in the mail message itself?

Answer 1

1)

SMTP-Based internet mail is a "store and forward" system, and the envelope sender mailbox of a message is the reverse path to which transport and pre-delivery processing errors are sent. Delivery status notification messages are sent by intermediaries and by delivery agents. Originators rely upon these others to send back to them.

IM Internet mail is not a "store and forward"system. Mail does not traverse a path to be delivered, and thereare no such things as "bounce messages" that travel back along thatpath.

2)

SMTP-Based Internet mail is a "recipient stores" system. Recipients maintain, and pay for, the storage for their mailboxes. Recipient mailboxes are stored in one single central place.

IM Internet mail is a "sender stores" system.The storage for each individual part of a recipient's mailbox is maintained, and paid for, by the originator of the particular message involved. Recipient mailboxes are distributed across one or more message stores.

3)

In SMTP-based Internet mail, every recipient provides their own In box and a sender's Out box is distributed across the storage paid for by all of the various recipients for each message.

In IM Internet mail, a recipient's In box is distributed across the storage paid for by the various senders of each message and every sender provides their own Out box.

4)

SMTP-based Internet mail is a "store and forward" system, with each "hop" on the path that a message traverses from originator to recipient recorded in one or more"trace" header.

IM is not a "store and forward" system. Mail does not traverse a path to be delivered, so there is no path to be traced in the first place.

5)

SMTP-based Internet mail also uses TCP port numbers in the "privileged" range, with well-known numbers. Only privileged user accounts may bind sockets to such ports. The parts of the MTS involved with providing TCP services have to have super user privileges, at the very least until they have opened a socket and bound it to the well-known port number.

IM Internet mail does not use well-known port numbers, and imposes no requirements that the TCP port numbers for its various services be in the "privileged" range. IM 2000 simply has no need for well-known port numbers:

The SMTP design can be pictured as:

+----------+ +----------+

+------+ | | | |

| User |<-->| | SMTP | |

+------+ | Client- |Commands/Replies| Server- |

+------+ | SMTP |<-------------->| SMTP | +------+

| File |<-->| | and Mail | |<-->| File |

|System| | | | | |System|

+------+ +----------+ +----------+ +------+

SMTP client SMTP server

i hope this helps you

Answer 2

from