Fix AutoComplete Issues in Outlook

To fix Outlook auto-complete issues, first ensure the feature is enabled under File > Options > Mail > Send messages by checking "Use AutoComplete List...".

If it is enabled but not working, try clearing the cache with the Empty Auto-Complete List button in the same menu, or remove individual entries by clicking the 'X' next to them.

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Important Notes:

• Cache Limit: The AutoComplete cache has a limit (typically 1,000 entries). Older entries may drop off.

• Server Sync: In Office 365, the list is often stored on the server, so working online for a while can refresh it.

• Remove Single Entries: Instead of clearing everything, remove specific problematic entries by clicking the 'X' next to them when they appear.