It doesn't crop up every day/week/month, isn't related to password or other issues specific to an account, and appears to be a problem with Outlook/Keychain interaction. This is an issue that has been around for several years going back to at least Outlook 2016 for Mac. Our users having trouble are using O365 accounts in combination with Duo (but Duo doesn't seem to be the problem). I wanted to add some notes about our workaround for this because sometimes just deleting those entries in keychain isn't (always) enough.
