I have encountered a bug with Smart folders (Outlook for Mac v16)
This is the only forum I could readily use to submit the bug since Microsoft doesn't seem to have an easy way to identify a bug. The bug has been present in numerous older versions; I just finally found the problem to a symptom I've had for years.
Smart Folders enables the use of search criteria to establish a view of emails as an alternate to the folders in which they reside. I have been using a simple smart folder with criteria "all mail received in the last ## days." I've been using 3 days. It turns out that, although the folder works most of the time, sometimes (approximately 10-20 times per day) the Smart Folder decides to ignore the ## of days and give me a view of ALL emails I've ever received. After it gets to the upper 10s of thousands (aided by the fan kicking on to cool the spike in processing), Outlook gives up the ghost and crashes. At long last I've found that if I use the "All received email in the last week," it works every time. Hasn't crashed since. I can deal with the extra four days worth of mail in the view. Saved my sanity. Anyway, hopefully a developer somewhere sometime will see this and fix the thing.

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