[Evolution] How to Import Mails from Icedove-Thunderbird to Evolution with lots of subfolders

[xuser092016 <michael s011235 gmail com>]

Hello,

I am using Evolution version 3.12.9 and have the following problem:
Until recent I have been using Thunderbird on Windows. Then I managed to
migrate to Debian Jessie 8.6 stable. Now, since I like Evolution best,
I'd like to import my mails to Evolution. 

Actually, I have already imported a mail via Import -> single file, but
I have got so many subfolders that importing everything by hand would be
tedious. 

Is there any script or any other way to import many mails in lots of
subfolders from Icedove to Evolution? 

I'd be glad at any help.

Best regards,
MichaelS