AutoComplete not working properly in Outlook 2013

Question

The AutoComplete List is a feature which displays suggestions for names and e-mail addresses as you begin to type them. These suggestions are possible matches from a list of names and e-mail addresses from the e-mail messages that you have
sent.
AutoComplete is a convenient feature when we send an email message, if it suddenly stops working, it becomes a real pain to the sender. If you encountered this problem, you can use the steps below to troubleshoot it and make it work again.
1. Check if the AutoComplete feature is turned on.
By default, the AutoComplete feature is enabled. If it isn’t working, of course the first thing to check is whether the feature is enabled. To check it, go to
File tab> Options > Mail, scroll down to the
Send Messages section and make sure the “Use Auto-Complete List to suggest names when typing in the To, CC, and Bcc lines” option is selected.
2. Check if AutoComplete works in OWA
Since Outlook 2010 and Outlook 2013 doesn’t store nicknames in .NK2 file, it stores the autocomplete cache in the user’s mailbox and caches to a local cache file. So, the OWA uses the same autocomplete list, we can log into OWA and check if AutoComplete
works.
If it works in OWA, it means the autocomplete list is OK. The problem lies in the Outlook client side. If the autocomplete doesn’t even work in OWA, the autocomplete list could be corrupt.
3. An Add-in may cause AutoComplete to not work correctly.
Problematic add-in may cause a number of issues in Outlook. If an add-in cause Outlook to crash, the AutoComplete lists could be affected and become corrupt.
To determine if a problematic add-in is the culprit, go to File > Options > Add-ins, disable all add-ins and then check if the problem continues. If the problem is gone with all add-in disabled, we can try re-enabling add-ins one-by-one to isolate
the problematic add-in:
(1) Start Outlook.
(2) On the File tab, click Options,
then click Add-Ins.
(3) In the bottom of the Outlook Options dialog box, make sure the
Manage drop-down shows COM Add-ins, and then click
Go.
(4) In the COM Add-Ins dialog box, select to enable an add-in and then click
OK.
(5) Repeat step 4 until you have all of the required Outlook functionality and Outlook remains stable.
If Outlook becomes unstable after re-enabling a particular COM add-in, disable that COM add-in and then contact the add-in vendor to see if they have an updated version that is more stable with Outlook.
For detailed steps about this, you can refer to the following KB article and look at the “Re-enabling COM add-ins one-by-one” section.
http://support.microsoft.com/kb/2934538
4. Reset the AutoComplete list.
If AutoComplete is enabled but still not working in OWA, it could be that the corruption within the AutoComplete list is causing auto-complete not to work correctly. You’ll need to manually delete the AutoComplete list to fix the issue.
Note: You will lose all addresses stored in AutoComplete.
If there is only one or several AutoComplete entries are corrupt, we can remove them by clicking ‘X’ or pressing
Delete key.
If all entries are corrupt, we can use one of the following two methods to delete the AutoComplete lists:
Method 1: Use the Empty Auto-complete List button.
1. Open Outlook.
2. On the File tab, click Options > Mail
tab.
3. Under Send Messages, click Empty Auto-Complete List.
It’s also recommended to untick the “Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines”.
4.  Restart Outlook and tick the “Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines” box again.
Test if the issue persists.
Method 2: Use the /CleanAutoCompleteCache switch.
1. Exit Outlook.
2. Press Windows key + R to open the Run command.
3. Type Outlook.exe /CleanAutoCompleteCache in the Run box and press
Enter.
5. Reach the maximum number of AutoComplete entries
Outlook limits the number of entries that you can save in the AutoComplete list. If you find some names unexpectedly removed from your autocomplete list, you may consider this situation.
Outlook 2013 has a limit of 1000 entries for the AutoComplete list. After you reach this limit, Outlook uses an internal algorithm to determine the best names to remove from the list. It does this based on a usage weighting. To avoid
this situation, you can use one of the following two methods:
Method 1: You can manually remove some AutoComplete entries that you no longer use. We can remove them by clicking ‘X’ or pressing
Delete key as we mentioned in portion 4.
Method 2: You can change the limit for the AutoComplete list by modifying the registry.
Because this configuration is untested, we do not recommended it. If you have a larger AutoComplete list, you could also lose a larger number of cached entries if your AutoComplete cache becomes unusable because of corruption. Given this disclaimer,
you can use the following registry data to increase the AutoComplete list limit in Outlook.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these
steps carefully. For added protection, back up the registry before you modify it.
1. Exit Outlook.
2. Start Registry Editor. Press the Windows key, type regedit and then press
Enter.
3. Add the following value:
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\AutoNameCheck
DWORD: MaxNickNames
Value: Type the number in
decimal form.
Note: Try increasing the limit by only a marginal amount to test the new limit. For example, to create a 20 percent increase in the limit in Outlook 2013, you would specify 1200 for the
MaxNickNames value.
4. Exit Registry Editor and restart Outlook.
More information
To avoid the risk of losing your AutoComplete list entries, it’s recommended to back up them regularly. In Outlook 2013, the AutoComplete list entries are stored in a hidden message in your default message store. To back up the entries, please follow
these steps:
1. Exit Outlook, and then close Outlook Web Access or Outlook Web App (OWA) on all workstations that are connected to your mailbox.
2. Download and install MFCMAPI here:
http://mfcmapi.codeplex.com
3. Run mfcmapi.exe.
4. Click Session > Logon.
5. Select your profile, and then click OK.
6. Select the data file that use your email address as the filename, and then double-click it.
7. Expand Root Mailbox, and then expand IPM_SUBTREE.
8. Find Inbox and right-click on it, and then click Open Associated Content Table.
9. In the newly opened MFCMAPI window, under the Subject column, right-click the item that has the subject
IPM.Configuration.Autocomplete, and then click Export Message.
10. In the Save Message To File window, select
MSG file (UNICODE) from the drop-down list, and then click
OK.
11. Select a folder location to which you want to save the message, and then click
Save.
If you have any questions and comments on this topic, please feel free to post here.
Please click to vote if the post helps you. This can be beneficial to other community members reading the thread.

Answer 1

Hi,
I'm marking the reply as answer as there has been no update for a couple of days.
If you come back to find it doesn't work for you, please reply to us and unmark the answer.
Regards,
Melon Chen
Forum Support
Come back and mark the replies as answers if they help and unmark them if they provide no help.
If you have any feedback on our support, please click
here