Are Mailbox Permissions Cumulative or Exclusive?

Hi, everyone.  Newbie to Exchange Administration...

I have noticed that Send On Behalf Permission can be set on the Outlook client or through the Exchange server.  Are permissions set through each location cumulative?

For example, if I grant Jane Doe Send On Behalf Of permission to my mailbox through the Outlook client, then grant John Smith Send On Behalf Of permission through Exchange PowerShell, will both Jane and John have Send On Behalf permission?  If not, which takes precedence?

Thank you for your thoughts on the matter.
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Alexei KuznetsovMicrosoft Outlook MVPCommented:
These are the same permissions.
alopez2Author Commented:
They are the same permission, but they were applied to two different people through different interfaces.  So, will both Jane and John have Send On Behalf Of permission?  Or will the Exchange permission overwrite the permission configured on the Outlook client?

I ask because people had been granted SOBO permission to a mailbox through the Outlook client.  However, when I granted someone else SOBO permission through Exchange, the original people ceased to have SOBO.  I found this odd, which led me to believe that permissions applied to a mailbox through Exchange overwrite permissions applied through the Outlook client.
alopez2Author Commented:
After doing some testing, looks like I figured out my own question.  Seems like all changes, whether done on Exchange side or Outlook client side, are applied in the same place.  Changes are cumulative, unless they override a previous permission for a user.  Will close out this question.

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Jackie Man IT ManagerCommented:
What is the difference between your answer and the answer of the expert above?
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