[HLUG] when ever sending large emails drops my net connectiion - why

[Mark Broadbent]

Hi Julian,

On 21/05/06, Julian Robbins <joolsr at fastmail.fm> wrote:
> ...
>
> If I sent an email over roughly, 500k, my IPCop ADSL net connection drops.

When you the connection drops, do you mean the actual ADSL modem
connection or just the logical TCP/IP connection between you and the
remote SMTP server dropped?

> I've no reason to suspect IPCop as this has been going on for many
> months, and i think it would have been fixed if it were a specific issue
> affecting IPCop.
>
> If i send the same mail via webmail its fine.

Webmail running remotely on the internet or locally on your network?

> I sent some tests via, my email smtp provider, fastmail.fm with and
> without SSL. I also tried it with my ADSL provider Pro-net, same
> problem, drops after getting only 21% through.

I might of been tempted to say the IPCop box was proxying your email
connections to do some sort of content/virus checking and has a file
size limit.   But if you've tried using SSL then this would throw some
warnings in Thunderbird about third party connection interceptions.

Also does the connection stop at exactly the same point, do you know
how much data has been transferred?

> I use IMAP with my email account, which is flawless apart from this.
>
> I'm using, FWIW Ubuntu Dapper, and Thunderbird 1.5.02, but I'm sure I
> had same problems, running Breezy and older version of Thunderbird.
>
> IPCop has been there all the way along.

Have you tried removing the IPCop box to check that isn't the cause.

> My only other inkling is could it be a MTU issue? we suspect Pro-net (or
> their upstream provider) are doing strange things with MTU which might
> cause issues, as we;ve had other strange ones occasionally.

If the IPCop box is just routing your data (i.e. no proxying) then you
can test this from your local machine by doing the following (on your
local machine not the IPCop box):

# ifconfig eth0 mtu 576

and then test (I know the MTU is very small but it will go through any
router at that size).

> I haven't tried connecting with my windows laptop yet, thsi might at
> least prove or disprove a couple of things.

Cheers
Mark

-- 
Mark Broadbent
Herefordshire LUG Master

* http://www.wetlettuce.com/
* http://www.herefordshire.lug.org.uk/

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