If not, go to the network monitor, enable logging on all rules, start Thunderbird and try to send or receive emails. After it fails, go back to the Network Monitor and turn off logging for all rules except the bottom one (which should be the block all rule).
If you then look at your logs you should be able to pick out the bits where it blocked Thunderbird. Post that chunk of the logs here and we’ll see what we can figure out.
Late yesterday I realised I could invoke System Restore and get back to where I was before all this happened. So I can’t do what you suggest. However I do still want to know what I did wrong. Probably misunderstood one of the warning messages Comodo keeps sending me.
I dug around in the logs, and found the following. I think it is the bit of the log you were referring to. Does it tell you anything? Or must I wait until this happens again? I could always undo the System Restore. :-((
If it helps, 192.168.1.2 is the address of the router I am using.