You need to provide more information on the account and its setup.

Thanks for your response. I have my email account with outlook.com The images uploaded are - TB1 shows Outlook folders. TB2 shows settings on TB client. TB3 shows TB mailbox folders. TB4 shows both sets of folders side by side. TB5 shows Imap settings on Outlook.com Am I wrong in assuming that folders on outlook.com and tb should be a mirror copy and that any updated data would amend both sets of folders. Hopefully i am explaining this clearly but I am being to think I am out of my depth! ☺

Check to see that all the folders are subscribed to in Thunderbird.

Yes David I did that but the missing folders dont appear in the subscription list either. I have tried re-installed TB but still the same. Its driving me up the wall!

If there are folders online and Thunderbird isn't showing them, then your only approach is to see if Outlook is restricting access. That is a feature of Gmail and might also be in Outlook.