Hi @Rudolf Amarlapudi ,
Do other users in the same organization have the same issue when using Auto-Fill entry to send emails to the same external user?
To confirm if the issue is related to the Outlook desktop client side, it is suggested for you to try the same operations on your web mail and see if the issue has any difference.
First of all, I would agree with the suggestions michev mentioned above, starting a new thread instead of replying to old emails and avoiding using the auto-complete entry of this user as much as possible should be able to help prevent this issue.
By the way, based on my experience, there is also some cached recipient information which is non-visible and may cause similar issues as well. We could try to delete them using the MFCMAPI tool:
- Download and extract the MFCMAPI tool, launch MFCMAPI.exe, click OK, on the Session Menu, click Logon, select the Outlook profile for the mailbox, click OK.
- Expand Root Container - Top of Information Store - Contacts - Recipient Cache, right click on it, choose Delete folder, click OK:
- Exit the MFCMAPI tool and restart your Outlook to test.
Hope these could help.
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