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Sorry I have already tried that. However rightly or wrongly I checked what processes were running and checked the unrecognized ones via Google.
The first one came back as indicating an error, I followed a link and found a company selling a PC checking software. I ran the trial copy which logged ober 250 errors across my PC, but the trial system did not deal with them all - it had to be purchased.
Since it was not too much money, I got it, ran it and cleared the errors.
Emails are now going as expected. Don't know if this is the right thing to do!