MDWS UPDATESorry not to reply but thought it better to concentrate on fixing things.... Thanks for all the comments and for bearing with me.
Good News - I'm hoping it's now all running again as intended from around 30 mins ago
Attempting to roll back the Window Updates (and some would not do so) despite using Safe Mode, resulted in a permanent startup reboot loop.. So decided on recovering a machine backup from a few days before the problems started, then updating to the 29th from various separate overnight data/code/sql dumps I have here to keep data loss to a minimum. I've made a few essential Window Updates with no bad effects but I will need to do more so restarts will be needed.
The main problem with the lack of alert mails seems to be with Windows Tasks - I won't go into it in detail but there are about 40 of them running in the backgroundand normally no problem. However sometime in the past month or so a number had stopped working or were erratic (but I hadn't made any changes via Task Scheduler). Task Scheduler itself says the are running with successful exit code (0x0) but the code within the php files isn't actually being run! If I take the php file and run it in a browser window it works okay.... Among them were three that handle the Upload Failure alerts, Resync Alerts and one that mails me other detected problems..... So for the moment they are being run separately in a browser.
I've also updated the Email client and this is now handled securely in both directions if supported at both ends.
Also reinstated Registrations which had been turned off.
User Too-SlowYou have a problem, apparently at your end but I don't know what it is causing it I'm afraid. I see this message occasionally from the Fast CGI process that handles the data uploads (one process allocated per upload) but in your case it's happening to a majority of your uploads today - maybe something timing out at your end?:
Partial results are valid but processing is incomplete: [client nn.nnn.nn.nnn:nnnnn] mod_fcgid: can't get data from http client
which results in no upload data.
Thanks