I don't understand. If you imported profile from old PC, why not just import it back to old PC? With the same mail accounts there would be no loss of messages. So, I must be missing something on what you did. Please share more info. Thank you.

I used the export tool to export the profile from the old PC, I then used import profile on the new PC, that worked fine. But I have now used the export tool on the new pc, I then used import on the old PC and nothing has been updated, the imported profile only has emails up to the date I stopped using it on the old PC, none of the newer emails that I got on the new PC are in the showing on the old one after I imported the new profile. Hope that makes sense ?

You are not giving full sentences of destinations of actions. If you export the profile on new PC and import on old PC, all messages should be there. Did you do that?

I did that And it hasn't worked

You exported profile from new pc to old pc. What didn't work?

I don't have any new messages showing.

Maybe the copy will work better if you exit thunderbird and copy profile from within Windows File Explorer, copying c:\users\<yourid>\appdata\roaming\thunderbird from new pc and pasting to c:\users\<yourid>\appdata\roaming on old PC. All messages should appear.

That worked Thank you very much for your help.

You are most welcome,