[ale] Problem with Earthlink's mail server

[Joe Steele]

On Wed, 23 Mar 2005, Christopher Fowler wrote:

> MY mail relay is having a serious problem with Earthlink's mail server. 
> In the old days a remote mail server would accept a file larger than
> allowed and then send a bounceback to the sender.  

This doesn't accurately describe how it is supposed to work.  If the
message is too large, the remote server does not accept it, nor does the
remote server send a bounceback. 

What should should happen is that the remote server rejects/discards the
message and returns a permanent failure (552) reply code.  It is then the
job of your server to generate a bounceback. 

> Earthlink does not do
> that.  It terminates the connection.  This causes sendmail to think
> there is a problem and then reties constantly.  

I doubt that Earthlink is intentionally dropping the connection as a
method for signaling that the message is too large.  This would make no
sense because, as you say, SMTP servers such as yours would repeatedly
hammer Earthlink's servers with retry attempts. 

Telneting to one of Earthlink's SMTP servers yields this
exchange:

| $ telnet mx1.earthlink.net 25
| Trying 207.217.125.16...
| Connected to mx1.earthlink.net.
| Escape character is '^]'.
| 220 mx-a065a05.pas.sa.earthlink.net EL_3_9_13_21 / ESMTP EarthLink SMTP
| Server Thu, 24 Mar 2005 06:52:58 -0800 (PST)
| ehlo test.com
| 250-mx-a065a05.pas.sa.earthlink.net Hello test.com [64.207.9.32], pleased to
| meet you
| 250-8BITMIME
| 250-SIZE 10485760
| 250 HELP
| 

As shown, Earthlink imposes a size limit of 10485760 bytes.  Your SMTP
server should recognize this and immediately bounce any message that exceeds
their limit without attempting to transmit it.  But any messages under this
limit should go through fine.

Bottom line is, a dropped connection should not imply that the message
size has exceeded administrative limits imposed by Earthlink.  I would
investigate other possibilities.  Do your mail logs contain any useful
info?  Perhaps tracing the TCP connection would shed some light on the
problem.

> Do you know what this
> does to the upload on a DSL connection.  My relay is on a RH 7.2 box and
> I'm finding myself setting the limit at the server no to 3M's just so
> this does not eat up my bandwidth.  Is there another alternative?
>

A possible short-term fix:  Relay all Earthlink-bound mail through your
ISP's servers, rather than through Earthlink's servers.  Connection failures
then become your ISP's problem, rather than yours.

--Joe