Using classic Outlook for Windows in business environments
To all affected users:
Microsoft has publicly acknowledged the problem - see the 03-Aug-2023 Microsoft support article Outlook Unexpectedly Prompts to Reopen Items From Your Last Session, which states in part:
STATUS: WORKAROUND
The Outlook Team is investigating this issue. We will update this topic when the fix status is available.
If the option does not appear in the Outlook Options and you want to disable it, you can set a registry key for the setting. Since the feature recurrently appears and disappears this may not be a comprehensive solution so it may or may not stop all occurrences of the issue.
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences
DWORD: ReopenWindowsOption
Value: 1
Kudos to b for posting about this support article today in the AskWoody thread Outlook MS Pro+ 2021 Start-up Options Disappeared.
Dell Inspiron 5584 * 64-bit Win 10 Pro v22H2 build 19045.3208 * Firefox v116.0.0 * Microsoft Defender v4.18.23050.9-1.1.23060.1005 * Malwarebytes Premium v4.5.34.275-1.0.2089 * Macrium Reflect Free v8.0.7279 * Microsoft Office 2019 Home and Business 2019 Version 2307 / Build 16626.20134 Click-to-Run