OnPrem impersonation requires mailbox on-premises

[jimthemcp]

When using an impersonation account that either doesn't have a mailbox or their mailbox is in EXO, you get the following error:
Could not open mailbox. Error:

Exception calling "Bind" with "2" argument(s): "The SMTP address has no mailbox associated with it."

This is a result of checking the credentials from this line:
CheckOnpremCredentials -ewsService $Service

which calls the function and fails here:
try {
$null = [Microsoft.Exchange.WebServices.Data.Folder]::Bind($ewsService, [Microsoft.Exchange.WebServices.Data.WellKnownFolderName]::MsgFolderRoot)
}

the mailbox not found exception could be used to validate the credentials as well, as it does show the connection succeeded

[dpaulson45]

@jimthemcp

Here is the FAQ on this.

https://microsoft.github.io/CSS-Exchange/Security/CVE-2023-23397/FAQ/#in-onprem-does-the-impersonation-account-need-to-have-a-mailbox