Exchange 2013 - Grant SendOnBehalf permission for Mailbox overwrites Existing permissions

By Przemyslaw Klys Exchange PowerShell January 22, 2016

Changing Send On Behalf setting in Exchange 2010 / Exchange 2013 or Exchange 2016 is quite simple task that can be easily done from GUI. It gets a bit more complicated when you try to add/change Send On Behalf rights from PowerShell.

❗ Problem Description

Usually most people will go for

Set-Mailbox <UserToAddPermissionsTo> -GrantSendOnBehalf <UserToGivePermissionsTo>

It's a simple command but it actually does a very dangerous thing… it overwrites current GrantSendOnBehalf permissions. While it's not a problem when it's first time you set it up, it's a big deal when there are already multiple people added to GrantSendOnBehalf field.

📧 Solution

Fortunately there's a simple way to do this to not overwrite this setting. Below you can find couple of commands that should make your life simpler.

function Add-DistributionListGrantSendOnBehalfTo { Param($newTrustee, $targetDistributionGroup)
    Set-DistributionGroup $targetDistributionGroup -GrantSendOnBehalfTo @{add=$newTrustee}
}
function Remove-DistributionListGrantSendOnBehalfTo { Param($oldTrustee, $targetDistributionGroup)
    Set-DistributionGroup $targetDistributionGroup -GrantSendOnBehalfTo @{remove=$oldTrustee}
}
function Replace-DistributionListGrantSendOnBehalfTo { Param($oldTrustee, $newTrustee, $targetDistributionGroup)
    Set-DistributionGroup $targetDistributionGroup -GrantSendOnBehalfTo @{add=$newTrustee}
    Set-DistributionGroup $targetDistributionGroup -GrantSendOnBehalfTo @{remove=$oldTrustee}
}
function Remove-MailboxGrantSendOnBehalfTo { Param($oldTrustee, $targetMailbox)
    Set-Mailbox $targetMailbox -GrantSendOnBehalfTo @{remove=$oldTrustee}
}
function Add-MailboxGrantSendOnBehalfTo { Param($newTrustee, $targetMailbox)
    Set-Mailbox $targetMailbox -GrantSendOnBehalfTo @{add=$newTrustee}
}
function Replace-MailboxGrantSendOnBehalfTo { Param($oldTrustee, $newTrustee, $targetMailbox) 
    Set-Mailbox $targetMailbox -GrantSendOnBehalfTo @{remove=$oldTrustee}
    Set-Mailbox $targetMailbox -GrantSendOnBehalfTo @{add=$newTrustee}
}

Simple usage of Exchange PowerShell commands from above:

Add-MailboxGrantSendOnBehalfTo -NewTrustee <AllowedUserToSendOnBehalf> -TargetMailbox <UserMailboxToManage>

Replace-MailboxGrantSendOnBehalfTo -NewTrustee <AllowedUserToSendOnBehalf> -OldTrustee <ReplacedUserToSendOnBehalf> -TargetMailbox <UserMailboxToManage>

Remove-MailboxGrantSendOnBehalfTo -OldTrustee <ReplacedUserToSendOnBehalf> -TargetMailbox <UserMailboxToManage>

Przemyslaw Klys / About Author

System Architect with over 14 years of experience in the IT field. Skilled, among others, in Active Directory, Microsoft Exchange and Office 365. Profoundly interested in PowerShell. Software geek.