[Dovecot] Discussion of new sending protocol proposal for IMAP

Marc Perkel marc at perkel.com
Thu Aug 18 21:23:54 EEST 2005


I joined the lemonade list for the new IMAP sending protocol and I mage 
the following suggestion about using IMAP as a front end for SMTP. The 
idea would be that a client could authenticate to IMAP, then ask for a 
tunnel to the SMTP server. - Here's my message. I thought I'd get people 


OK thanks. I would clarify what I'm proposing.

I looked at the current proposal and what I'm proposing might be in 
addition to rather than instead of the current proposal. LDELIVER as it 
is now offers capabilities of sending messages and forwarding 
attachments without downloading them, leaving more power on the server 
side. This is important for mobile clients with limited power on the 
client end.

What I'm suggesting is something in addition to LDELIVER where we add 
SMTP-TUNNEL as a capability. This is for laptop users who have to deal 
with finding an outgoing smpt server and who might be behind a firewall 
that blocks smtp ports.

What is different about my proposal is that what I'm suggesting isn't a 
straight pass through at the beginning. The client has to talk to IMAP, 
then authenticate, and then upon successfil authentication would ask for 
an SMTP connection to the local smtp server. At that point it is a 
tunneled connection.

1) This allows the IMAP ports to be used for SMTP and avoid port blocking.
2) It uses the same IMAP authentication for SMTP so outgoing SMTP nee 
not be configured separately. It merely acts as an authenticated condiut 
to get to SMTP.
3) It would in no way interfere with future advancements in SMTP 
technology at others were concerned about.
4) Client and server recoding would be trivial.
5) This could be used in place of SMTP-AUTH and would eliminate the need 
for authenticated SMTP making server smtp configuration easier.

So - if you look at it as an addition then you don't have to choose 
between them.

Stephane Maes wrote:

> Marc,
> Based on the suggestions that we have received so far, we will publish 
> a proposed update. We are looking at smtp proxy options.
> Note that LDELIVER contributes also in supporting server side 
> recomposition with upload of only body / header part diffs. I am not 
> sure that tunneling would allow this. But I am looking into it.
> Thanks
> Stephane
> PS I still have an action item to provide the use cases / reasons / 
> pros of using it. I will distribute soon on the list.
> _____
> Stephane H. Maes, PhD,
> Director of Architecture - RTCC & Mobile, Oracle Corporation.
> Ph: +1-203-300-7786 (mobile/SMS); Fax / UM: +1-650-607-6296.
> e-mail: stephane.maes at oracle.com
> IM: shmaes (AIM, Y!,Skype) or stephane_maes at hotmail.com (MSN Messenger)
> -----Original Message-----
> From: lemonade-bounces at ietf.org <lemonade-bounces at ietf.org>
> To: lemonade at ietf.org <lemonade at ietf.org>
> Sent: Thu Aug 18 08:41:10 2005
> Subject: [lemonade] Outside the box suggestion about Lemonade
> Hello,
> I'm Marc Perkel - and I'm new to this list. I run a span filtering 
> service called junkemailfiltercom and do some web hosting.
> I've read sme of the discussion about LDELIVER and I just wanted to 
> throw out a wild idea and see where it goes.
> The Problem: Sending email without having to separately config 
> outgoing SMTP so that an IMAP connection can be used especially by 
> moble users to send email.
> So - suppose that instead of adding something complex - why not just 
> establish a tunnel to SMTP over IMAP?
> Here's what I propose. The client when sending email would establish a 
> second IMAP connection to the server. One of the CAPABILITIES will be 
> SMTP-TUNNEL. After sending the command the IMAP server opens a 
> connection to the SMTP server and acts as a straight pipe through 
> until the connection is closed.
> The advantage of this is that you can take your existing SMTP code and 
> instead of connecting it on port 25 you connect it on port 143. Then 
> everything you could do with SMTP is available. You would just need to 
> add a smal layer to the SMTP layer to authenticate to the IMAP server 
> and tell it to open a tunnel to the SMTP server. On the server side 
> you just connect to localhost:25 or whatever you configure it to and 
> pass data.
> Basically what I'm suggesting is that IMAP act as a tunnel to SMTP 
> providing and authenticated connection using the same credentials as 
> the imap client uses.
> Unless I'm missing something - and I might be - seems to me this would 
> be dirt simple to implement and wouldn't impose any of the limitations 
> to the SMTP protocol that other people here are concerned about.
> Who likes this idea?
> _______________________________________________
> lemonade mailing list
> lemonade at ietf.org
> https://www1.ietf.org/mailman/listinfo/lemonade

Marc Perkel - marc at perkel.com

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