My pleasure -
Even though Outlook officially supports IMAP-IDLE, I kindly offer you to test both T-bird and Outlook to be open at the same time.
Send an email to yourself, and 99% of the time, T-bird will receive the email faster than Outlook (which both support idle...so...)
The problem becomes much more prominent in low-memory machines. Outlook takes up far more memory, and the less RAM your computer has to spare, the longer Outlook takes to receive those IDLE messages. Just something we've noticed...the same is not true for T-bird.
I'm sure part of the reason is that T-bird is nowhere as bloated as Outlook