Outlook 365 Classic Autocomplete gone strange

This functionality was simply removed in the latest release of Outlook.

I created a post in the Microsoft Feedback Forum to restore this functionality.  Please help by upvoting it!

https://feedbackportal.microsoft.com/feedback/idea/97490d3b-7d45-f111-9a91-000d3a05c4f5

Hi @Hornblower409 @David Baker 

My apologies for the confusion in earlier response.

In my initial test environment, I was still observing the X behavior. After testing in other environments, I realized that the behavior is actually consistent with what you described in version 2604 (Build 19929.20086). My original test environment is still on version 2603 (Build 19982.20182) and has not yet been updated, which explains the discrepancy.

Version 2603 (Build 19982.20182)Version 2604 (Build 19929.20086)

I’m also just a fellow user, and my earlier testing was incorrect. As forum moderators, we don’t have access to Microsoft’s backend or internal systems to intervene in product features. We can only verify and confirm observed behavior based on testing and expected functionality.

Hi @David Baker 

Since this is a public platform, I’ve moved the detailed description to a private message to avoid exposing any personal or organizational information. Please refer to the private message for those details.  

From your description, it’s very possible that the Hotmail account being configured as a Microsoft Exchange account is contributing to the issue. The behavior you’re seeing aligns closely with how Outlook’s AutoComplete can act when multiple data sources get mixed after updates.  

Starting Outlook in Safe Mode only disables add-ins and custom extensions, so it wouldn’t affect profile-level data or server-side recipient suggestion behavior. Since the issue persists in Safe Mode, that helps rule out add-ins as the cause.  

To test this without rebuilding the entire profile, you can try the following: 

1.Sign out of Outlook completely, close the app, then reopen and test AutoComplete.  

2.Test by temporarily removing the Hotmail (Exchange) account 

-Remove that one account (don’t delete profile) 

-Restart Outlook 

-Test AutoComplete 

If the behavior returns to normal, that strongly indicates the Exchange-backed account is influencing AutoComplete for the whole profile. You can then re‑add the account cleanly and monitor whether the suggestions rebuild correctly.  

Please let us know how it goes or if you need further guidance.       

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.  

In classic Outlook, suggested recipients in the To/Cc/Bcc fields come from the AutoComplete (nickname) cache and, in newer builds or when connected to Exchange Online, may also be influenced by Microsoft Search. When the list starts surfacing unexpected or very old entries and the delete “X” is missing, the supported controls are:

1. Verify AutoComplete is enabled
   1. Go to File → Options → Mail.
   2. Under Send messages, ensure “Use Auto-Complete List to suggest names when typing in the To, Cc, and Bcc lines” is checked.
2. Remove individual bad entries (when supported)
   1. Open a new email.
   2. Type the first few characters of the unwanted suggestion.
   3. When it appears, hover over it until it is highlighted.
   4. Select the X icon (if present) or press Delete.
   If the X is not present and Delete does nothing, this indicates the suggestion is not coming from the local AutoComplete list in the classic way (for example, it may be coming from Microsoft Search when connected to Exchange Online). In that case, only the “Enable/Disable AutoComplete” and “clear list” options apply; per the documentation, other AutoComplete management options do not apply when Microsoft Search is driving suggestions.
3. Clear and rebuild the AutoComplete list
   1. In File → Options → Mail, under Send messages, use the option to clear the AutoComplete list (this is the supported method to reset the nickname cache).
   2. After clearing, send new messages to the correct recipients so Outlook can rebuild the list with current addresses.
4. Understand list limits and unexpected removals Outlook limits the number of AutoComplete entries (for Outlook for Microsoft 365 and recent perpetual versions, the limit is 1,000 entries). When the limit is reached, Outlook removes entries based on usage weighting. This can cause older or less-used entries to disappear and others to remain, but it does not by itself explain the inability to delete entries; that behavior is tied to how suggestions are being provided (classic AutoComplete vs Microsoft Search).

If Outlook is connected to an Exchange Online mailbox and is on a build where Microsoft Search powers the To/Cc/Bcc suggestions, only the following from the AutoComplete documentation apply:

• Enabling/disabling AutoComplete.
• Removing entries one at a time (when the UI exposes the X/delete behavior).

Other legacy methods (direct file manipulation, etc.) are not supported and may not affect what is shown.

Given that Safe Mode behaves the same and profile recreation is undesirable, the practical options within supported behavior are:

• Keep AutoComplete enabled but periodically clear the list and let it rebuild from current usage.
• If the suggestions remain unusable, disable “Use Auto-Complete List to suggest names…” and rely on the address book/contacts search instead.

For more background on how the AutoComplete list works, its limits, and the supported ways to enable and clean it, see the referenced articles.

References:

• The Outlook AutoComplete list
• Manage suggested recipients in the To, Cc, and Bcc fields in Outlook
• Outlook replies or forwards cause non-delivery error “Your message did not reach some or all of the intended recipients”
• When creating a Quick Step for New E-mail To, Outlook does not save it