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Running Outlook on the iMac causes the screen to flicker and eventually black out and reduce to half/split screen display.
If I don't run the Outlook app the Mac runs like clockwork.
With Outlook active, at some point the flickering begins and then gets progressively worse until the screen is completed fuzzed or it pops back to a half black screen (which continues to flicker intermittently - more often than not)
Whilst it sounds like a hardware issue (and I've ordered a new Mac thinking it was!) it appears to be tied to Outlook.
iMac (Retina 5K, 27-inch, Late 2015)
3.3 GHz Intel Core i5
8 GB 1867 MHz DDR3
AMD Radeon R9 M395 2048 MB
Mac OS 10.14.1 (18B75)
Outlook 16.19
Rebooting seems to clear it until we run Outlook again, then the cycle continues.
Using older versions of Outlook for Mac for personal email and calendar
Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.
I updated to Catalina just over 1 week ago and I am pleased to confirm that this has resolved the issue. I no longer have to use outlook in low resolution mode
Took a white , but at last resolved!!
I have interim due to the issues moved across to Apple Mail where I at this point will remain ,however good to know fixed.
I had exactly the same issue. After reading the various replies, I checked out the Outlook issue mentioned. My Outlook automatically launches, but I quit the application prior to launching anything else (Photoshop) and, hey presto - no flickering, no blackouts. I hope that the issue is now resolved for good. I intend uninstalling my office 365 applications which won't be that convenient, but as I was on the verge of buying a new imac, it is a small sacrifice. Many thanks to those who suggested that Outlook might be causing the problem.