You start typing a name in the To field and Outlook suggests nobody, so you type full email addresses again and again. The good news: the AutoComplete feature is rarely broken for good. Work through these fixes in order and the suggestions come back - without losing anything you cannot afford to lose.
Outlook remembers the people you email and offers their names as you type. That memory is called the AutoComplete List, and when it stops working the cause is almost always one of three things - the setting got switched off, the cache file is damaged, or the profile is damaged. This guide fixes them in that order, safest first, and warns you about the one tempting button that makes things worse.
Everything else is wasted effort if this one checkbox is off. Outlook can suggest names only while the feature is enabled:
This box sometimes gets unticked by an update, a repair, or someone cleaning up settings. Checking it takes twenty seconds and fixes a surprising share of cases on its own.
AutoComplete only remembers people you have actually emailed from this profile, and it needs a few letters before it can match:
Honest note: a brand-new PC, a new profile or a freshly installed Outlook always starts with an empty list. That is normal behaviour, not a fault - the list fills up again as you send mail.
In classic Outlook the suggestions live in one small cache file. When that file gets damaged, suggestions stop even though the setting is on. Restarting it is the standard fix:
%LOCALAPPDATA%\Microsoft\Outlook\RoamCache and press EnterStream_Autocomplete_ and ends in .dat.old at the end - do not delete itBe clear about the cost: the fresh file is empty, so old suggestions do not come back on their own. They rebuild one by one as you email people. The renamed .old file keeps the old data on disk, and our separate guide on moving AutoComplete shows how it can be restored or carried to another PC.
If the cache restart did not help, the damage is usually in the profile itself rather than in the list:
If suggestions work in the new profile, the old profile was the problem - keep the new one. Your mail itself is untouched by this test, because IMAP and Microsoft 365 mail lives on the server.
Next to the AutoComplete checkbox sits a button labelled Empty Auto-Complete List. Many people press it while hunting for a fix. Do not. It deletes every remembered name permanently and does not repair anything - a damaged cache file stays damaged, only now it is damaged and empty. The rename method in Fix 3 achieves the clean restart while keeping the old file as a backup. There is a full page below on what that button actually destroys.
Every fix on this page, shown live on screen - the setting, the cache file restart and the profile test, in the exact order to try them.
▶️ Watch Full VideoThe three usual causes are the AutoComplete checkbox getting unticked, the Stream_Autocomplete cache file in the RoamCache folder getting damaged, or profile corruption after an update or crash. The setting check takes twenty seconds, and renaming the cache file fixes the second cause, so work through the fixes in order rather than reinstalling Outlook.
No. The AutoComplete list is a private memory of addresses you have typed or received mail from - about a thousand names at most. Your contacts are a separate address book you manage yourself. A person can be suggested by AutoComplete without being in your contacts, and a saved contact may not appear in AutoComplete until you have actually emailed them.
The old suggestions stop appearing because Outlook builds a new, empty cache. But renaming is not deleting - the old file stays on disk with a .old extension, and it can be restored or moved to another computer with the documented copy method. Deleting the file, or pressing Empty Auto-Complete List, is what destroys it permanently.