Re: Current status?

In article <7h%vk.609$393.335@trnddc05>, John Santos <john@xxxxxxx> writes:
Bill Gunshannon wrote:
In article <g9pl82$lh7$4@xxxxxxxxx>,
helbig@xxxxxxxxxxxxxxxxxxxxxxxx (Phillip Helbig---remove CLOTHES to reply) writes:

In article <t_Wvk.2076$U5.1028@xxxxxxxxxxxxxxx>,
=?ISO-8859-1?Q?Jan-Erik_S=F6derholm?= <jan-erik.soderholm@xxxxxxxxx>
writes:



Yup. I think that many of the problems arise because MUAs use the same
protocol (SMTP) and port (25) to send mail to MTAs as MTAs use to relay
mail to each other.

Modern MTAs can be configured to allow mail clients to submit mail to them on
the mail submission port (port 587) rather than port 25. See RFC 2476
http://www.faqs.org/rfcs/rfc2476.html


On the other hand MTAs talk to MUAs (when delivering
mail) using either of 2 different protocols (that I know of), POP3 on
port 110 and IMAP on port 143. (I don't think anything does POP2 on
port 109 any more.)

Logically there are three parties involved not two.
MTA, MUA and Message store.

The MTA delivers mail to another MTA or to a message store.
The MUA originates mail and sends it to a MTA.
Mail clients generally incorporate the above MUA functionality together with
the ability to display and manipulate mail in the message store.

POP and IMAP are protocols used to access and manipulate the message store.
They are NOT used to deliver mail to the message store.

Note.

The SMTP servers which come with the TCPIP stacks (TCPWARE, MULTINET or TCPIP
SERVICES/UCX) are NOT fully fledged modern MTAs. For that you would need either
PMDF or MX.
(
PMDF is a commercial product but is available free for hobbyist use.
MX is now an open-source free product see
http://www.madgoat.com/
However I'm not aware of anyone currently continuing development of MX.
)


David Webb
Security team leader
CCSS
Middlesex University


I think if the mail origination and mail relay
functions and protocols had been kept distinct from the start, everything
would be much cleaner and under better control. For example, the way
you want to authenticate a mail originator is very different from the
way you want to authenticate a mail transport agent.

In their defense, SMTP is a "push" protocol (both for originating and
relaying mail), but POP3 and IMAP are "pull" protocols, so there's a
lot more commonality between an MUA sending to an MTA, and an MTA
forwarding mail to another MTA, than between them and mail delivery.
Also, these protocols originated before SPAM was an issue.


--
John Santos
Evans Griffiths & Hart, Inc.
781-861-0670 ext 539
.

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