Sent Item showing duplicate send item for an mailbox

lalajee 1,811 Reputation points

I have created new mailbox using below command

New-RemoteMailbox -Name $DisplayName -Alias $Alias -OnPremisesOrganizationalUnit $OU

Then connect to Office 365 and run below command

Set-Mailbox -Identity "HR@keyman .com" -MessageCopyForSentAsEnabled $true
Set-Mailbox -Identity "HR@keyman .com" -MessageCopyForSendOnBehalfEnabled $true

Then On Office 365 Mailbox/Delegation
added Full access, Send As, Send On behalf permission for the group

Now when I try to send an message from outlook using new mailbox I can see 2 records in sent item

If I change Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\Preferences\DelegateSentItemsStyle from 1 to 0 then this stops.

This mailbox has over 100 users and all of them are having same issue.

I would like to know why this is happening and if they is anyway I can fix it remotely without modifying the registry

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Accepted answer
  1. KyleXu-MSFT 26,201 Reputation points


    Those two emails are copied by "DelegateSentItemsStyle" and "MessageCopyForSentAsEnabled/MessageCopyForSendOnBehalfEnabled"

    I check in my lab, the "DelegateSentItemsStyle" key doesn't exist by default.

    So, if you enable this key on your client, and don't want to disable this one. You will need to disable the MessageCopyForSentAsEnabled and MessageCopyForSendOnBehalfEnabled on this mailbox. In this way, there will not exist duplicate emails.

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