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List:       kmail-devel
Subject:    Re: Smart SMTP
From:       Malte Starostik <malte () kde ! org>
Date:       2002-10-25 0:51:11
[Download RAW message or body]

Am Donnerstag, 24. Oktober 2002 08:46 schrieb Ed White:
> Hi,
>
> I got this idea:
> automagically use the MX SMTP to deliver mail.
>
> What does it means ?
[snip]
> We can speedup things and void local SMTP adding the option to connect
> _directly_ to the destination SMTP.
>
> Example:
>
> From: me@myself.com
> To:	you@yourself.com
>
> When you click "send", KMail looks for the MX record via DNS for the "To"
> domain.
> MX:	1.2.3.4
> Now the KMail connects to that SMTP and relay your mails using classic
> "commands".
>
>
> What about ? ;-)
>
> 	Ed
>
> P.S. I read somewhere on the net that there's a Win client that already do
> this, but I couldn't find it.
Hi Ed,

I see two problems with this approach, the first of which can be solved, the 
second cannot:

1) There's a little bit more to direct sending than just look for an MX record 
and send to that server. You'd have to check for all MX records, take into 
acount their priority and try them according to this list until you found a 
working server. (which basically means duplicating code that already exists 
in any MTA)

2) This is the real showstopper - many sites use MAPS DUL or similar 
blacklists to disallow dialup clients to send directly to their mail 
exchanger in order to reduce SPAM. This is because spammers often send 
directly from their dialup lines to avoid problems with abusing their ISPs 
MTA or having to look for open relays.

Once upon a time I had my local sendmail configured to send mail directly to 
the recipient's mail exchanger but noticed very soon that this was a bad idea 
because many messages were returned because I'm on a line listed in DUL. I've 
been using my ISPs MTA as smarthost since.

Just my 2e-2€
-Malte

PS: there's another reason to use a local *) MTA: it's usually faster to pump 
a message to a host on your LAN or to your ISP than to some MX on the other 
side of the globe.

*) either really local or at your ISP's

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