[Evolution] Importing mbox file in Evolution

[André Ockers <andre ockers eu>]

Dear Evolution users,

As I've moved from Icedove (Thunderbird) to GNOME Evolution, I want to 
transfer the mail from an older account that's in Icedove "local 
folders".
So here [1] is what I officially should be doing and I also read this 
[2].

The first thing that suprises me is that when trying to import the mbox 
file, Nautilus doesn't offer me the option to view hidden files.
So I copied the mbox file to /tmp (so that it wouldn't be a hidden file 
anymore).
Now when I select that file in Evolution, the standard "Outlook" option 
is automatically selected and all the other options, including mbox, are 
greyed out.
The continue-button is also greyed out so I'm basically stuck at that 
point.

Please help, thank you very much in advance.

Best regards,

André Ockers

[1] 
https://help.gnome.org/users/evolution/stable/import-apps-mozilla.html
[2] 
https://www.debuntu.org/how-to-import-thunderbird-emails-to-evolution/