Invoke-MailboxAudit

Grab all Exchange permissions of a user, bulk of users or all users on the tenant.

Tested against O365 Exchange Online.

Supported permissions:

MailBox level (assigned by tenant/mailbox administrator)
SendAs
SendOnBehalf
Folder (Top of Information Store, Inbox, Sent Items, Calendar, etc). These are user-assigned permissions.

You can use this module to list out all mailboxes where users gave Read (Owner, FullAccess, etc) permissions to Everyone or similar roles, thereby exposing their mailbox to other members in the organization.

Usage

Use Windows PowerShell 5.1.
Install the module by invoking it or dot-sourcing it:

iex((iwr https://raw.githubusercontent.com/daniel0x00/Invoke-MailboxAudit/master/Invoke-MailboxAudit.ps1 -UseBasicParsing).content)

Run the cmdlet as shown below.

MFA support: Does your admin account use multi-factor authentication? Then load this script under a "Microsoft Exchange Online Remote PowerShell Module" special Windows PowerShell console and use the -MFA switch when using the cmdlet.

List all the permissions for 'user2', 'user5', 'mike'

PS C:\> $c = Get-Credential
PS C:\> 'user2','user5','mike' | Invoke-MailboxAudit -Credential $c -Verbose | Format-Table -AutoSize

User                          GrantedUser                                    AccessType                                        Permission                            Details
----                          -----------                                    ----------                                        ----------                            -------
user2@cditest.onmicrosoft.com Default                                        Folder:Inbox (Inbox)                              Owner
user5@cditest.onmicrosoft.com Default                                        Folder:Top of Information Store                   ReadItems, FolderOwner, FolderVisible
user5@cditest.onmicrosoft.com Default                                        Folder:subIBX - rare& \characters (User Created) DeleteOwnedItems
user5@cditest.onmicrosoft.com "outside@domain.com" [SMTP:outside@domain.com] ForwardRule                                       Enabled                               If the message:...
user5                         mike@cditest.onmicrosoft.com                   MailboxPermission                                 FullAccess
user5                         user2@cditest.onmicrosoft.com                  MailboxPermission                                 FullAccess
mike@cditest.onmicrosoft.com  user5, user2                                   SendOnBehalf                                      Granted
mike                          user2@cditest.onmicrosoft.com                  MailboxSendAs                                     SendAs
mike                          user5@cditest.onmicrosoft.com                  MailboxSendAs                                     SendAs
mike@cditest.onmicrosoft.com  user2                                          Folder:Inbox (Inbox)                              Editor

List permissions for given users at bulk using a MFA admin account and under a proxied network

Note: The -Proxy switch forces the cmdlet to use the default proxy settings configured on the computer where the cmdlet runs.

PS C:\> $c = Get-Credential
PS C:\> Import-Csv .\Users.csv | Invoke-MailboxAudit -Credential $c -MFA -Proxy -SkipMailboxPermission -SkipForwardingRules -Folder Inbox,Calendar,SentItems -Verbose

List all the permissions for users with a mailbox that starts by: a*

PS C:\> $c = Get-Credential
PS C:\> Invoke-MailboxAudit -Credential $c -Identity a* -SkipMailboxPermission -Verbose

List all the permissions for all users in the tenant, for the Inbox and Sent Items folders, skipping all child user-created folders as well as forwarding rules

PS C:\> $c = Get-Credential
PS C:\> 97..(97+25) | select @{n='Identity';e={[char]$_+'*'}} | Invoke-MailboxAudit -Credential $c -Proxy -SkipMailboxPermission -SkipUserCreatedFolder -SkipForwardingRule -SkipSendAsPermission -Folder Inbox,SentItems -Verbose

daniel0x00 / Invoke-MailboxAudit