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O365SupportKapil's avatar
O365SupportKapil
Copper Contributor
Apr 13, 2020

Issue in SendOnBehalfTo

I Have a client having issue while trying to sendonbehalf email from Shared Mailbox which end user have SendOnBehalfTo permission. When he select From address following error occurred and email not d...
O365SupportKapil's avatar
O365SupportKapil
Copper Contributor
Apr 30, 2020

VasilMichev Thanks for you response.

I opened a case with MS and I knew that - how should it work..

this is what MS responded...

Recommended Next Steps:

When a shared mailbox is added as a New Account, Send on Behalf permissions won't work. Send on Behalf permissions only work when the account is auto mapped or added under the advanced mailbox settings.

For one user, please remove the permissions for the shared mailbox and then add the permissions back using the following PowerShell Command: 

  • Add-MailboxPermission -Identity "Shared Mailbox" -User "User to Add" -AccessRight "Permissions to mailbox" -InheritanceType All -AutoMapping $True

After the permissions have been applied and the mailbox automatically mapped in Outlook, please test the send of behalf permissions

Also, on the same user's machine, after the shared mailbox has been automatically mapped, please run the advanced Outlook diagnostic: https://support.microsoft.com/en-us/help/4098558/scan-outlook-by-using-microsoft-support-and-recovery-assistant

Marko_Stevcic's avatar
Marko_Stevcic
Copper Contributor
Mar 16, 2021
The simplest way to resolve this is to empty Outlook cache folder (AppData\Local\Microsoft\Outlook\RoamCache) and not use autocomplete form.
*Back up the cache files so that you can restore the files if something goes wrong.
Manually enter the email address you want to send the message to, or find the person you want to send mail to from the GAL.

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