Sorry if it seems i’m asking silly questions, I’ve never used the Imap library, so i’m just following basic troubleshooting hoping it helps you 
did you get something like this in your log? I’m guessing not or you would have mentioned it:
Importing test library 'ImapLibrary' failed
the next question is: is there at least 1 tab or 2 spaces in front of Open Mailbox and Close Mailbox
Like this:
imap test 1
Open Mailbox server=outlook.office365.com/../… user=skjdhfjksdhjkf password=skjdhfkjdshf
Close Mailbox
Not like this (This will cause “Test case contains no keywords” regardless which library you use):
imap test 2
Open Mailbox server=outlook.office365.com/../… user=skjdhfjksdhjkf password=skjdhfkjdshf
Close Mailbox
Dave.