Jose-Marcio Martins da Cruz wrote:
SM wrote:
There is no need for a new reply code if the text after the reply code
is structured. You still have to determine how to relay the new address
back to the MUA as SMTP does hop by hop delivery. HTTP, on the other
hand, requires a direct connection between the server and the user
agent. Even if there is a proxy in the middle, the user agent still has
access to the HTTP reply code.
The idea is why, in this case, SMTP can't work the same way as HTTP ? The
goal is, if wanted, be
able to not work in "store and forward" mode or ("hop by hop", as you say).
The existing use of SMTP "store and forward" (to another MTA) is perhaps
primarily to shield internal MTAs from external access.
Eg: To get to me, you have to hop thru several MTAs:
1) The spam filtering engines
2) The sendmail perimeter array
3) The Exchange cloud
4) The mailbox server
2-4 aren't connected to the Internet, and we don't want them to be for
security reasons.
(1) is effectively not a store-and-forward MTA to (2) (it's analogous to
a packet relay). Secondly, we may be eliminating (2) in the
not-to-distant future. However, we still don't want anything but (1)
directly connected to the Internet. An HTTP-style redirect won't work.
Similarly, on outbound, you have to traverse thru several mail servers,
each with different functionality, funnelling thru a couple very
specific outbound-only servers. You don't want redirection to the
outbounds directly.
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