SMTP->Windows connection with 2.4.16

SMTP->Windows connection with 2.4.16

[Andy Jeffries]

Hi Guys,

A friend of mine is having a problem connecting to Blueyonder's SMTP
server with a 2.4.16 Kernel.  He has helpfully provided the following
information to illustrate the problem.  Is this a known issue with 2.4.16?
 Can anyone help?  If so, what more information do you need (tcpdump
output, .config file, ...?)

# telnet smtp.blueyonder.co.uk 25 

Connection refused

# ping smtp.blueyonder.co.uk

Replied normally

# telnet <any other mail server including Telewest's inbound one> 25

Worked fine

# nmap -sS -P 25 smtp.blueyonder.co.uk

Showed the port as open

# nmap -sT -P 25 smtp.blueyonder.co.uk

Showed the port as closed

After this, he rebooted back in to the RedHat 2.4.9 Kernel (RedHat 7.2
with updates applied) and it was all fine.  Unfortunately he had already
fired off a nasty email to Blueyonder's tech support (but it serves them
right for running a Microsoft server).

Cheers,


-- 
Andy Jeffries                   | Scramdisk Linux Project
http://www.scramdisklinux.org   | Lead developer

"testing? What's that? If it compiles, it is good, if it boots up 
 it is perfect."
  --- Linus Torvalds

Re: SMTP->Windows connection with 2.4.16

[Alan Cox]

> server with a 2.4.16 Kernel.  He has helpfully provided the following
> information to illustrate the problem.  Is this a known issue with 2.4.16?

Nope

>  Can anyone help?  If so, what more information do you need (tcpdump

tcpdump data

> # telnet smtp.blueyonder.co.uk 25 
> Connection refused
> 
> # ping smtp.blueyonder.co.uk
> Replied normally

Quite reasonable. smtp servers stop listening when under high load

Alan

Re: SMTP->Windows connection with 2.4.16

[David Woodhouse]

lkml@andyjeffries.co.uk said:
> A friend of mine is having a problem connecting to Blueyonder's SMTP
> server with a 2.4.16 Kernel.

Their firewall is broken. See http://gtf.org/garzik/ecn/ but note that it's
fairly out of date - ECN actually became a Proposed Standard months ago, and
for Blueyonder to _still_ be running a broken firewall is a particularly
spectacular display of incompetence.

--
dwmw2

Re: SMTP->Windows connection with 2.4.16

[Thomas Langås]

Alan Cox:
> Quite reasonable. smtp servers stop listening when under high load

That actually depends on what type of MTA you're using.

-- 
Thomas