Using older versions of Outlook for Mac for personal email and calendar
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.
I am having exact the same problem as above also on my 27" iMac ( late 2015 )
This has only happened since Outlook update 16.25 .
Reverted back to 16.24 and has not happened since .
We live in hope that this has solved the issue for me until it is fixed.
By the way- since Word 16.25 update a small window will open in left corner and not full window - here too, had to revert to 16.24 which works fine .
All in all , Office version16.25 appears to be a bit messed up !
Thanks for the information will try outlook 16.24
Best Regards
Richard