I have had many problems with thunderbird

What problems?

So, I exported my email messages

What are you trying to achieve in the first place?

I had problems with the calendar and events mainly. I never received and notification of new email or events. Enail notification not to much of a worry but event a big worry.

So, I thought I would start again but this time I would manually set up everything insead of auto imports.

I managed to import the calendar but can find no way to import the email messages to my new profile.

I intend to delete to old profile which was set up auto. when my new profile is working. If I cannot be happy with the running of thunderbird I must return to outlook which I used for many years. I am trying to leave all microsoft software.

Install this add-on. https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

You can then import the mbox files (no file extension) from the old profile.

I found that title when reading about importing and I searched addons for it but it was not found.

I have installed it and have been able to import the current inbox.

When I ty to import messages which were saved in separate folders under the inbox all I get so far is a list of folders such as 34SP.com.mozmsgs and China.mozmsgs. Each of the folders has the correct name but are empty!

I have moved the 11 empty folders to trash and am currently looking for a way to import these folders and their contents.

Edit\; they are empty in the mail program but are not empty in the saved file.

I have found out how to do what I want but have final questions:

Is there a limit on the size of the messages and data stored?

Does the size affect the operation (slow down) the program?

Thank you for your prompt assistance.

Edit: I have just remembered one important problem I had:

Having allowed TB to auto. instal settings from outlook I was later unable to find anywhere to change settings such as passwords etc. There was only a one mage manage settings and identities.

Also I have now found a spurious folder which cannot be deleted:

20150416174740.13477.45976.repoze.sendmail%40worker2.prl.nu.wdseml