Autofill contacts not detected by name in New Outlook

Hi @Rob Gloss,

Thank you for your response.

Outlook’s auto‑complete and name‑resolution features rely on correctly structured contact properties such as Display Name, FileAs, email fields, and MAPI identifiers. In many cases, contacts exported from Thunderbird contain incomplete or mismatched name fields, which prevents Outlook from recognizing them properly. As a result, the auto‑complete cache (Outlook’s NK2‑equivalent) won’t store recipients if the underlying contact record is missing required attributes.

For reference, you may find this article helpful: Autofill contacts not detected by name in New Outlook – Microsoft Q&A.

To address this, I recommend re‑exporting and re‑importing your contacts using clean column mapping, as Thunderbird’s CSV headers don’t always align with Outlook’s expected schema:

1. Export your contacts from Thunderbird as a CSV file.
2. Open the CSV in Excel.
3. Ensure the column headings correctly map to:

• First Name
  • Last Name
  • Email Address
  • Display Name
  1. Import the updated file into Outlook via: People > Your contacts > Import Contacts.

If any of these fields are empty or mismatched, Outlook won’t be able to resolve names when typing. If fixing a single contact restores auto‑complete for that entry, it confirms the imported CSV/VCard contained incomplete name data, and you may need to clean up the remaining contacts in the same way.

If the issue persists, you should request your IT admin to raise a support ticket to Microsoft Support Agent. This issue may present as a complex case that required back-end logs for further troubleshoot. Given the nature of the problem, the most effective next step is use your admin credentials to submit a support request through the Microsoft 365 Admin Center. This route ensures that a Microsoft support engineer can initiate a remote session to investigate backend configurations, run advanced diagnostic tools, and, if necessary, escalate the case to specialized teams with access to internal systems and logs. These backend resources are essential for resolving issues that go beyond what’s visible in the user interface.

As community moderators, we’re here to guide you, but due to privacy and security limitations, we don’t have access to the backend tools required for a full resolution. For this reason, contacting Microsoft Support via the Admin Center is the most secure and efficient way forward.

I sincerely recommend you create a support ticket from Microsoft 365 Admin Center > Support > Help & Support.  

Microsoft also provides customer service phone numbers based on your region. You can find the appropriate contact number here: Customer service phone numbers - Microsoft Support 

For your security, please do not reply to this thread with this case number information. The official support line is the only secure way to handle these details. 

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.    

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you. 

I look forward to continuing the conversation. 

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Hi @Rob Gloss,

Thank you for reaching out to Microsoft Q&A Forum.

According to Manage suggested recipients in the To, Cc, and Bcc fields in Outlook - Microsoft Support, AutoComplete works differently in New Outlook because New Outlook for Windows no longer uses the old NK2 AutoComplete cache. Suggestions in To/CC/BCC fields are powered by Microsoft Search and Contact Suggestions, not the legacy AutoComplete list. Imported contacts from Thunderbird often lack proper Display Name or indexing, so name-based suggestions fail while email-based suggestions work. AutoComplete is now cloud-based, syncing across Outlook and OWA.

It relies on your Microsoft account contacts, people suggestions from recent communication and search indexing in Windows and Outlook 

 You can try the following steps to see if you can recover your autofill contact:

1. Verify Contact Storage

• Go to People view in New Outlook.
• Ensure contacts are saved under your Microsoft account (not local PST) since New Outlook does not support local-only contacts. 

2. Rebuild Search Index

• Navigate to Settings (Win + I) → Privacy & Security → Searching.

• Ensure Outlook is included in indexing.
• Click/tap on Advanced indexing options under Related settings.

You can now close the Settings if you like. Click/ tap on Advanced.

Click on Rebuild.

Tap OK to confirm.

Indexing will now be in progress. Rebuilding the index might take a long time to complete. If needed, you can click/tap on Pause to stop rebuilding the index.

You can click close when you see the indexing has completed.

Note: There is no manual AutoComplete cache reset in New Outlook, the feature is cloud-driven.

Alternatively, you can also rebuild it with BAT file.

I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

I look forward to continuing the conversation.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.