It sits right beside the AutoComplete checkbox, labelled like a helpful reset. It is not one. The Empty Auto-Complete List button permanently deletes every email address Outlook has learned for you - and it is one of the most commonly regretted clicks in Outlook. Read this before your mouse goes anywhere near it.
Most people meet this button while trying to fix autofill, not destroy it. The name sounds like clearing a browser cache - tidy, harmless, reversible. It is none of those. This page explains plainly what the button deletes, why it cannot repair a broken list, what to do if it was already pressed, and the two situations where pressing it is genuinely the right call.
The Empty Auto-Complete List button, found at File > Options > Mail in the Send messages section, wipes the AutoComplete cache down to zero entries the moment you confirm the prompt. Every name Outlook has learned - clients, colleagues, the accounts department, that one supplier whose address nobody can spell - is removed in a single click. It is not a reset, not a refresh and not a repair. It is a deletion, designed for situations like handing a PC to a new employee or clearing a hopelessly polluted list on purpose.
People reach for this button because their suggestions stopped working, reasoning that a clean slate must help. It cannot. If suggestions stopped because the cache file is damaged, emptying it leaves the same damaged file - now with nothing in it. If the cause was the checkbox or the profile, the button changes neither. The failure that sent you hunting stays exactly as it was, and you have traded a broken list for no list at all. The rename-the-file restart in our main fix guide is the correct clean-slate method, because it forces Outlook to build a new file - and keeps the old one as a backup.
Be honest with yourself about the three possibilities:
Stream_Autocomplete file or a backup copy still sits there - our disappeared-list guide covers the rename recovery.The button has a legitimate job - it is just a narrow one. Press it when you are deliberately retiring a machine or account and the next user should not inherit your address memory, or when a list is so polluted with one-off and wrong addresses that curation would take longer than rebuilding. Even then, copy the cache file to a safe place first, so the decision stays reversible for a week. Any other situation - one wrong name, a slow suggestion box, a troubleshooting hunch - has a smaller, safer tool. For one wrong name that tool is the X on the suggestion row.
The video shows exactly where this button hides, what its confirmation prompt really means, and the safer restart method you should use instead.
▶️ Watch Full VideoNo undo exists inside Outlook. For Exchange and Microsoft 365 accounts the list is stored in the mailbox, so check quickly whether another device still shows the old list. For IMAP and POP accounts, recovery is only possible if an older Stream_Autocomplete cache file still exists in the RoamCache folder or in a backup - otherwise the list rebuilds only by sending mail again.
No. It deletes only the AutoComplete memory - the suggestion list. Your contacts folder, your emails and your account settings are untouched. That is some comfort, but for heavy email users the suggestion list itself is a real productivity asset built over years, which is why the loss stings.
Only if the list is beyond saving. A middle path exists: first copy the current Stream_Autocomplete cache file somewhere safe, then empty the list. If the fresh start feels worse after a week, the rename recovery can bring the old list back. Without that two-minute backup, the decision is permanent the moment you click.