We started having problems more than a week ago, with queues of 10K and more building up over the day through to Xtra.  At night, this was 2-3 times as bad. 
 
We managed to (finally) get through to CTSHelp, who advised us that Xtra had made a policy decision to only accept 2 connections per source IP/domain. This was effectively throttling our mail down to around 2-3 messages per second. 
 
Obviously an attempt to limit the impact of the recent Sober work and variants on xtra's part...
 
Paul
 
Date: Fri, 23 Apr 2004 16:33:12 +1200
From: jamesc@wave.co.nz (James Clark)
Subject: Re: [nznog] Xtra
To: Neil Gardner < NeilG@renaissance.co.nz>
Cc: nznog@list.waikato.ac.nz
Message-ID: < 20040423043312.GA27729@phoenix.wave.co.nz>
Content-Type: text/plain; charset=us-ascii

On Fri, Apr 23, 2004 at 04:10:01PM +1200, Neil Gardner wrote:
> Chuckle - I _KNOW_ it's just a coincidence, but less than 15 minutes after
> lampooning Xtra's generally useless status page about never being updated,
> they have managed to list the intermittent (!) email problem, only 26 hours
> after it was first notied on this list!

26?  Try more than 48 hrs, and apparently it was worse on Tuesday!