Cannot send email to contact from Outlook Address Book

Hi @Diane Shachter

Thank you for sharing your concerns. 

Based on my research, this issue is commonly related to an outdated Offline Address Book (OAB), cached recipient data, or a corrupted Outlook profile. 

You may refer to the Microsoft article below for detailed troubleshooting steps: How to troubleshoot the Outlook Offline Address Book in a Microsoft 365 environment - Microsoft Sup… 

Additionally, if the issue only occurs with specific recipients, please try checking and recreating the affected contact: 

Open Contacts (or People) in Outlook. 

Locate the affected contact and double‑click to open it. 

Make sure the Email address field contains only the email address (no extra spaces, no display name, no legacy Exchange strings). 

If there are multiple email fields or old Exchange entries, please create a new contact with only the correct email address and test again. 

This helps ensure Outlook resolves the recipient using the correct SMTP address instead of cached or legacy address information. 

I hope this helps. 

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

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