Outlook autocomplete not working: how to fix it on Windows 11

Applies to: classic Outlook for Windows (Microsoft 365, 2024, 2021, 2019 and 2016) and new Outlook for Windows. Outlook on the web keeps its own suggestion list, and Outlook for Mac has separate settings.

Match your symptom

What you see	Possible cause	Go to
No suggestions at all in classic Outlook	Auto-Complete option turned off	Fix 1
An old or misspelled address keeps being suggested	Stale entry in the list	Fix 2
The X doesn’t remove an entry	The entry is a saved contact, or a current issue	Fix 2, Known issues
Names you used before have vanished	1,000-entry limit reached	Fix 3
New recipients are never remembered	Damaged AutoComplete cache	Fix 3, Fix 4
Suggestions gone after a new PC or profile	List tied to the mailbox or data file	Fix 5
Suggestions differ between apps	Each app keeps its own list	Fix 5
A colleague’s name never appears	Not in your contacts or the address list search	Fix 6

Where Outlook’s suggestions come from

Knowing the source of a suggestion tells you where to fix it. According to Microsoft Learn’s article The Outlook AutoComplete list, classic Outlook builds an AutoComplete list, also called the nickname cache, as you send email. It holds the addresses and display names of people you’ve written to and drives both name completion and automatic name checking in the To, Cc and Bcc lines. In Outlook 2010 and later, the list is stored as a hidden message in your primary mailbox or data file instead of the old .nk2 file.

There’s an important exception on the same page. From Outlook for Microsoft 365 Version 2202, if you’re connected to an Exchange Online mailbox, suggestions come from Microsoft Search. In that case Microsoft says only two parts of its guidance apply: turning the feature on, and removing entries one at a time. Emptying the list or changing its limit may then make no visible difference.

New Outlook for Windows works differently. Microsoft’s page Manage suggested recipients in the To, Cc, and Bcc fields in Outlook says its suggestions come from your personal contacts, organization contacts such as the Global Address List, and names you’ve used before. It shows up to five matches and narrows them as you type. Microsoft Learn also notes that classic Outlook’s list isn’t shared with Outlook on the web, which keeps its own.

Fix 1: Make sure suggestions are turned on

In classic Outlook, Microsoft Learn gives these steps:

1. Select File > Options.
2. Select the Mail tab.
3. Scroll to Send messages and make sure Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines is checked, then select OK.

If the box is already checked, clearing it, closing Outlook and checking it again is a harmless way to rule out a setting that didn’t save. That’s general guidance rather than a Microsoft step.

In new Outlook, the Microsoft support page links to a section on turning off or resetting suggested contacts, but doesn’t list those steps on the same page. As general guidance, open Settings (the gear icon) and type “suggested” in the settings search box to find the option, then make sure it’s turned on. If your PC is managed by work or school, an administrator can control some of these settings.

Fix 2: Remove a wrong or outdated suggestion

A suggestion that points to an old address, a typo or someone who has left will keep coming back until you remove it. Microsoft Learn’s steps for classic Outlook:

1. Open a new email.
2. Type the first few characters of the name or address.
3. When the entry shows in the suggestions, point at it so it’s highlighted, but don’t select it.
4. Select the X that appears, or press Delete.

This removes the entry from AutoComplete only. Microsoft notes it can still show up in search boxes, and it returns to the list if you email that address again. The new Outlook page adds two more reasons a name can come back: saved personal contacts keep appearing until you delete the contact, and organization contacts keep appearing until an administrator removes them. So if the stale address is stored on a contact card, edit or delete it there too.

A stale entry can also make mail bounce even when the address looks right, because the classic list stores Exchange details along with the address. If that’s what sent you here, our guide to the 550 5.1.10 RecipientNotFound bounce covers the sending side.

Fix 3: Names disappear or new ones aren’t remembered

Microsoft Learn lists a limit of 1,000 entries for Outlook for Microsoft 365, Outlook 2019 and Outlook 2016. Once the list is full, Outlook uses usage weighting to decide which names to drop, so names you haven’t emailed for a while can disappear without warning. Microsoft’s advice is to remove entries you no longer need, so the ones you rely on keep their place.

If Outlook stops adding new people at all, the same page says the cache may be damaged. Try removing a few entries one at a time first (Fix 2). If that doesn’t help, empty the whole list (Fix 4).

Microsoft also documents a registry value that changes the limit, but calls raising it untested and not recommended, and warns that a large damaged cache can lose many entries at once. Leave it alone unless your IT team asks for it.

Fix 4: Empty the whole AutoComplete list

Warning: this deletes every saved suggestion in classic Outlook. Your contacts aren’t affected, but you’ll need to type full addresses until Outlook learns them again. On an Exchange Online mailbox with Version 2202 or later, Microsoft says this method doesn’t apply because suggestions come from Microsoft Search.

Microsoft Learn gives two ways to do it. In Outlook, go to File > Options > Mail, then under Send messages select Empty Auto-Complete List and confirm with Yes. Or close Outlook, select Start, then Run (or press Windows+R) and enter:

outlook.exe /CleanAutoCompleteCache

If Outlook isn’t in its default location, Microsoft says to give the full path to Outlook.exe. Our guide to resetting Outlook to default settings lists this switch alongside the other cleanup options, in case more than suggestions are misbehaving.

Fix 5: Suggestions missing after a new PC, profile or app

Because classic Outlook keeps the list in your primary mailbox or data file, it’s tied to that store rather than to the PC. As general guidance, a new profile connected to the same mailbox may keep its suggestions, while a profile that starts with a new local data file begins with an empty list. Microsoft has a separate support article, “Import or copy the Auto-Complete list to another computer”, for moving the list or importing an old .nk2 file.

Switching apps matters too. Classic Outlook’s list isn’t shared with Outlook on the web, and new Outlook draws on contacts, the organization’s address list and earlier recipients, so it won’t show exactly the same names as classic. If you rely on classic Outlook’s list and moved to new Outlook recently, our guide on getting classic Outlook back explains the toggle.

To carry important people across every app, save them as contacts. The new Outlook page lists personal contacts as a source of suggestions, so they don’t depend on any one cache.

Fix 6: The person never shows up as a suggestion

New Outlook shows only up to five matches, so a name may simply be lower down. Keep typing the surname or the email address to narrow the list. If the person still doesn’t appear, Microsoft’s new Outlook page suggests the address book:

1. Select Address book in the ribbon, or the To, Cc or Bcc button in the message, to open Add recipients.
2. Choose your personal contacts or the Global Address List.
3. Type a name in Search this list of contacts. If the list looks blank, Microsoft says the address list likely has more than 500 entries, so typing is needed to start a search.
4. Select the person, then select Save.

If a colleague isn’t in the Global Address List at all, only an administrator can add or fix that entry.

Fix 7: Update or repair Outlook

If suggestions still fail after the checks above, refresh the app. These are general troubleshooting steps rather than steps from the Microsoft pages cited here:

1. Close Outlook completely, then open it again.
2. Install Office and Windows updates, then restart the PC.
3. Run a Quick Repair of Office, as described in our guide to repairing Microsoft Office.

For keyboard shortcuts and other time-savers once suggestions work again, see our Outlook tips and tricks.

Known issues

Microsoft lists confirmed Outlook problems on its Office known-issues pages. If removing an entry with the X in Fix 2 has no effect, or suggestions stopped working right after an update, search Microsoft Support for current Outlook known issues before you empty the whole list.

Related guides

• 550 5.1.10 RecipientNotFound: how to fix the Outlook bounce
• How to reset Outlook to default settings (classic and new Outlook)
• How to repair Microsoft Office (Quick Repair and Online Repair)
• Classic Outlook download: how to get it back on Windows 11 and 10
• Outlook tips and tricks: 12 ways to manage email faster in Outlook for Windows

Official sources

• Microsoft Learn: The Outlook AutoComplete list
• Microsoft: Manage suggested recipients in the To, Cc, and Bcc fields in Outlook