Exchange Online Powershell Add / Remove delegated mailbox

Connect to Exchange Online PowerShell

https://docs.microsoft.com/en-us/powershell/exchange/exchange-online/connect-to-exchange-online-powershell/connect-to-exchange-online-powershell?view=exchange-ps

Set-ExecutionPolicy RemoteSigned

$UserCredential = Get-Credential

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

Import-PSSession $Session -DisableNameChecking

**Run this AFTER you are finished any of the commands below**

Remove-PSSession $Session

**To See Mailboxes**

Get-Mailbox

How to add / remove automapping for a shared mailbox in Office 365

(Add delegated mailbox in Outlook)

https://support.microsoft.com/en-us/help/2646504/how-to-remove-automapping-for-a-shared-mailbox-in-office-365

To do this, follow these steps:

Connect to Exchange Online by using remote PowerShell. For more info about how to do this, go to the following Microsoft website:
Connect to Exchange Online Using Remote PowerShell
Remove full access permissions for the user from the mailbox. This removes automapping. To do this, at the command prompt, type the following command, and then press Enter:
```
Remove-MailboxPermission -Identity <Mailbox ID1> -User <Mailbox ID2> -AccessRights FullAccess 
```
Note In this command, <Mailbox ID1> represents the mailbox to which the user is granted permissions, and <Mailbox ID2> is the mailbox of the user from whom you want to remove full access permissions.

For example, to remove full access permissions for an administrator from John Smith's mailbox, use the following command:
```
Remove-MailboxPermission -Identity johnsmith@contoso.onmicrosoft.com -User admin@contoso.onmicrosoft.com -AccessRights FullAccess 
```
After you run this command, you're prompted to confirm the action:
Confirm
Are you sure you want to perform this action?
Removing mailbox permission "johnsmith@contoso.onmicrosoft.com" for user "admin@contoso.onmicrosoft.com" with access rights 'FullAccess'".
[Y] Yes [A] Yes to All [N] No [L] No to All [?] Help (default is "Y"): y
Grant full access permissions back to the user for the mailbox, but don't enable automapping. To do this, at the command prompt, type the following command, and then press Enter:
```
Add-MailboxPermission -Identity <Mailbox ID1> -User <Mailbox ID2>-AccessRights FullAccess -AutoMapping:$false 
```
Note In this command, <Mailbox ID1> represents the mailbox to which the user is granted permission and <Mailbox ID2> is the mailbox of the user to whom you want to add full access permissions.

For example, to add full access permissions for an administrator to John Smith's mailbox, type the following command, and then press Enter:
```
Add-MailboxPermission -Identity johnsmith@contoso.onmicrosoft.com -User admin@contoso.onmicrosoft.com -AccessRights FullAccess -AutoMapping:$false
```