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

[Andrew Hodgson]

Hi,

MTU is the probable issue here.  The main MRU/MTU setting to use on BT
exchanges is 1500, with the MSS set to 1460.  Lowering the MTU is needed
on some ISPS, for example I had a friend on virgin.net who had exactly
the same problem, and I put the MTU to 1430 and it worked better.

Andrew.

-----Original Message-----
From: herefordshire-bounces at mailman.lug.org.uk
[mailto:herefordshire-bounces at mailman.lug.org.uk] On Behalf Of Julian
Robbins
Sent: 21 May 2006 12:27
To: Herefordshire Linux Users Group.
Subject: [HLUG] when ever sending large emails drops my net connectiion
- why

Hi

Hope the mtg went ok, list seems quiet these days !!

I've had a ongoing problem , i want to fix - any suggestions, fixes 
gratefully recd!

If I sent an email over roughly, 500k, my IPCop ADSL net connection
drops.

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.

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 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.

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.

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

Any ideas ??

Julian Robbins



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