Step 1:

Step 2:

Step 3:

Press CONTINUE .
Thunderbird will estimate the connection, then you must select CONFIGURE MANUALLY

Step 4:

Employees, students and external workers who have an account on Office365 (the username is in the format username@cvut.cz):

Confirm DONE, A verification table will pop up.

 

Step 5:

Approve app permissions on O365