It is theoretically possible that the server problem caused a routing table issue and that for some reason TalkTalk's routers/switches have a duff routing table following that. In that case it would be TalkTalk that would have to resolve it by refreshing the routing.
My highest accolades go to Ian72 who was spot on with his diagnoses! This morning it was observed that emails were flooding into our mobile devices and sure enough a trace route now completes whereas prevously it failed:
Tracing route to ns31.sovdns.com [126.96.36.199]
over a maximum of 30 hops:
1 29 ms 29 ms 28 ms 192.168.134.1
2 47 ms 79 ms 45 ms host-62-24-254-203.as13285.net [188.8.131.52]
3 46 ms 46 ms 45 ms host-78-151-228-51.as13285.net [184.108.40.206]
4 47 ms 46 ms 46 ms host-78-151-228-56.as13285.net [220.127.116.11]
5 47 ms 47 ms 47 ms host-78-144-9-65.as13285.net [18.104.22.168]
6 47 ms 48 ms 48 ms uk.slo.ld5.101.r1.misp.co.uk [22.214.171.124]
7 52 ms 49 ms 48 ms uk.slo.prgn.aggr.sw1.misp.co.uk [126.96.36.199]
8 56 ms 50 ms 49 ms uk.slo.prgn.b10.stk1.misp.co.uk [188.8.131.52]
9 47 ms 47 ms 47 ms ns31.sovdns.com [184.108.40.206]
The turning point to success was an email from TalkTalk on 15 December 2017 at 08:21 which read:
I apologise that previous agents have not grasped the issue you are having. I agree there seems to be a routing issue. I have put the trace routs to our network team to investigate.
And amazingly, within 24 hours the problem was sorted.
We lost our email service on 29th November and obviously contacted our hosting provider Vidahost to resolve the issue. Testing over the next few days illustrated that the problem was well and truly with TalkTalk and a ticket was opened with them on 5th December. Meanwhile the previous day a VPN connection was established to another user who was a BT subscriber to enable us to receive and send emails. No re-configuration of Outlook was required as we use the email servers of Vidahost and not those of TalkTalk.
TalkTalk’s repeated assertions over the next two weeks or so, was that as it was an email issue with another provider, a resolution was only possible by them (Vidahost) despite us demonstrating it was a routing issue within the TalkTalk network, Sensing that we were in a deadlock position we decided to start the process off of migrating to another ISP with our choice being Cloudscape. The migration date is set for 29th December. As it will be a like for like service and Cloudscape will save as money, there seems little point in pulling the plug on this migration.
We now know that a more clued up TalkTalk Business support service could have solved the problem almost instantly but failing to do so has lost them a customer. For sure we our considerably out of pocket with the whole sad affair and thoughts turn to compensation, but there is no chance on that front!