I am having a similar issue with v10.0.2045.0 causing a 10-15 second slowdown when previewing or opening any attachments in Outlook 365. Disabling real time scanning or pausing all protection is the only way to alleviate the issue. Disabling client email integration does not help, nor does disabling Defender via PS command or GPO, full reinstall of Office/ESET, different Outlook profiles or safe mode. I eventually landed on disabling the real time scanning of outlook.exe, while still leaving all email client integration enabled, and attachments load with speed now.
The laptop in question is a Lenovo Thinkbook.
Any insight is appreciated, thanks!
