Outlook’s autocomplete feature — officially called the AutoComplete List, sometimes referred to as the nickname cache — is one of those things you only notice when it stops working. The moment it disappears, suddenly every email requires you to type out full addresses from scratch, dig through your contacts, or risk sending messages to the wrong person entirely. If Outlook has stopped suggesting email addresses as you type in the To, CC, or BCC fields, this guide covers every known cause and fix, from a simple settings toggle to recovering your cache after a PC migration.
\n\n\n\nWhat Is the Outlook AutoComplete List?
\n\n\n\nThe AutoComplete List is a local cache of email addresses and display names that Outlook remembers every time you send an email. As you start typing a name or address into the To field, Outlook queries this cache and drops down a list of matching suggestions. The more you use Outlook, the more useful these suggestions become.
It is worth understanding that the AutoComplete List is entirely separate from your Contacts or your organisation’s Address Book. Those are proper stored records. The AutoComplete cache is simply a record of addresses you have typed and sent to previously — think of it as muscle memory for your email client. In older versions of Outlook (2003 and earlier) this data was stored in an NK2 file. In modern versions of Outlook (2010 onwards, including Microsoft 365), it is stored as a stream file within your Outlook profile’s RoamCache folder on your local machine.
\n\n\n\nBecause the cache is stored locally, it is tied to your Windows user profile and your Outlook profile on that specific machine — which is why so many autocomplete problems arise after a PC migration or profile rebuild.
\n\n\n\nCommon Reasons Autocomplete Stops Working
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- The AutoComplete feature has been switched off in Outlook’s settings, either manually or following an update \n\n\n\n
- The cache has been deliberately cleared or has become corrupted \n\n\n\n
- A new Outlook profile was created, which always starts with an empty cache \n\n\n\n
- The Address Book or Global Address List search is taking priority over the local cache \n\n\n\n
- You recently migrated to a new PC and the cache was not transferred \n\n\n\n
- The cache has hit its maximum size limit of 1,000 entries, causing older entries to be dropped as new ones are added \n
Fix 1 — Enable AutoComplete in Outlook Settings
\n\n\n\nThe first thing to check is whether autocomplete has simply been turned off. This is a single checkbox in Outlook’s options and is surprisingly easy to accidentally disable.
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- Open Outlook and click File in the top left corner. \n\n\n\n
- Click Options at the bottom of the left panel. \n\n\n\n
- In the Outlook Options window, select Mail from the left sidebar. \n\n\n\n
- Scroll down to the Send messages section. \n\n\n\n
- Make sure the checkbox labelled “Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines” is ticked. \n\n\n\n
- Click OK and test by composing a new email. \n
If this checkbox was already ticked and autocomplete still is not working, move on to the fixes below.
Fix 2 — Clear and Rebuild the AutoComplete Cache
\n\n\n\nIf autocomplete is enabled but showing incorrect, outdated, or corrupted entries, the best approach is to wipe the cache entirely and let Outlook rebuild it from scratch. You will lose your existing suggestions, but they will be replaced with accurate ones as you send emails going forward.
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- Go to File > Options > Mail. \n\n\n\n
- Scroll to the Send messages section. \n\n\n\n
- Click the Empty Auto-Complete List button. \n\n\n\n
- Confirm the prompt by clicking Yes. \n\n\n\n
- Click OK to close Options. \n
After clearing the cache, Outlook will begin rebuilding it automatically as you send new emails. Every address you type and send to will be added back over the coming days and weeks.
\n\n\n\nFix 3 — Delete Individual Wrong Entries
\n\n\n\nIf the cache is mostly fine but contains a handful of wrong or outdated addresses — for example an old email address for a contact who has since changed jobs — you do not need to clear the entire list. Outlook lets you remove individual entries without touching the rest of the cache.
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- Start composing a new email and begin typing the address you want to remove in the To field. \n\n\n\n
- When the incorrect suggestion appears in the dropdown, use the arrow keys to highlight it. \n\n\n\n
- Press the Delete key on your keyboard. \n\n\n\n
- The entry is immediately removed from the cache. \n
This is particularly useful for addresses that Outlook keeps suggesting even though you never intend to email that person again, or for old addresses that keep appearing alongside a contact’s correct, updated one.
\n\n\n\nFix 4 — The Cache Did Not Transfer to Your New PC
\n\n\n\nBecause the AutoComplete cache is stored locally rather than in your mailbox, it is one of the things that does not come across automatically when you set up Outlook on a new computer. Your emails, calendar, and contacts will all sync normally through Exchange or Microsoft 365, but your AutoComplete cache stays behind on the old machine.
\n\n\n\nIf you still have access to your old PC, you can copy the cache manually. The cache files are located in the following folder on Windows:
\n\n\n\n%LOCALAPPDATA%\\Microsoft\\Outlook\\RoamCache\\
\n\n\n\nYou can paste this path directly into Windows Explorer’s address bar to navigate there. The files you need are named starting with Stream_Autocomplete. Copy the entire RoamCache folder from the old machine and paste it into the same location on the new one. Close Outlook before copying and reopen it afterwards. Your autocomplete suggestions should then be restored.
\n\n\n\nFix 5 — Outlook Profile Was Recreated
\n\n\n\nIf your IT team rebuilt your Outlook profile, or if Outlook prompted you to create a new profile and you did so, your AutoComplete cache will have been left behind on the old profile. A fresh profile always starts with an empty cache.
\n\n\n\nIf the old profile files are no longer accessible, the only option is to let the cache rebuild naturally over time. As you send emails, each unique address you type and send to will be added back to the list. For most people, the cache feels reasonably populated again within a few weeks of normal email use. If Outlook is also running slowly during this period, it may be worth checking for other performance issues at the same time.
\n\n\n\nFix 6 — Address Book Search Is Conflicting
\n\n\n\nIn some organisations, particularly those using Microsoft Exchange or Microsoft 365 with a large Global Address List, Outlook may prioritise searching the server-side address directory over the local AutoComplete cache. This can make autocomplete feel sluggish, show unexpected results, or appear not to be working at all when really it is the Address Book that is responding instead.
\n\n\n\nYou can adjust which address source Outlook queries first by changing the search order in your account settings:
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- Go to File > Account Settings > Account Settings. \n\n\n\n
- Click the Address Books tab. \n\n\n\n
- Select the address book you want to adjust and click Change. \n\n\n\n
- Under “When sending email, check names using these address lists in the following order”, use the arrow buttons to reorder the list. \n\n\n\n
- Click OK and restart Outlook. \n
Placing your Contacts higher in the order ensures that local suggestions appear before the Global Address List results.
\n\n\n\nAutoComplete vs Contacts vs Address Book
\n\n\n\nOne source of ongoing confusion is that Outlook can pull address suggestions from three completely different places, and it is not always obvious which is which.
\n\n\n\nThe AutoComplete List is the local cache discussed throughout this article — a record of every address you have previously typed and sent to. It is fast, personal, and stored on your machine.
\n\n\n\nYour Contacts are the people you have explicitly saved in Outlook’s People section. These sync with your Microsoft 365 account and are available across devices. Outlook will also suggest contacts as you type, which is why you sometimes see suggestions appear even for addresses you have never emailed before — they are already in your saved contacts.
\n\n\n\nThe Address Book (or Global Address List in an Exchange environment) is a directory maintained by your organisation. It contains every person in your company and is managed centrally by your IT team. If you regularly email the same groups of people, creating a distribution list in Outlook can save time regardless of how your autocomplete is configured. Autocomplete issues and spell check problems are often both linked to Outlook settings that have drifted from their defaults after an update or profile change.
\n\n\n\nFrequently Asked Questions
\n\n\n\nHow long does it take for the AutoComplete cache to rebuild after being cleared?
\n\n\n\nThere is no set timeframe — it depends entirely on how many emails you send and to how many different addresses. Outlook adds one entry per unique address each time you send. If you send 20–30 emails a day to a varied set of recipients, your cache will feel useful again within a week or two. If you email the same handful of people repeatedly, it may take longer to fill up with the range of addresses you need.
\n\n\n\nCan I transfer my AutoComplete list to a new computer?
\n\n\n\nYes, as long as you still have access to the old machine. Navigate to %LOCALAPPDATA%\\Microsoft\\Outlook\\RoamCache\\ on the old PC, copy the Stream_Autocomplete files, and paste them into the same location on the new machine. Close Outlook before transferring and reopen it once the files are in place. If you no longer have access to the old machine, you will need to let the cache rebuild from scratch.
\n\n\n\nWhy does an old or wrong email address keep appearing in suggestions?
\n\n\n\nThis happens because the address is still stored in your AutoComplete cache. To remove it, start typing the address in the To field, use the arrow key to highlight it in the dropdown, and press Delete. If the address continues reappearing, it may be stored in your Contacts as well — in which case you will also need to update or delete the contact record in Outlook’s People section.
\n\n\n\nDoes AutoComplete work with shared mailboxes?
\n\n\n\nThe AutoComplete cache is tied to your individual Outlook profile, not to the mailbox you are sending from. If you send emails from a shared mailbox, those addresses will be added to your personal cache as normal, and suggestions will appear when you compose from that shared mailbox in future. However, the cache is not shared with other users who have access to the same shared mailbox — each person builds their own local cache independently.
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