Setup mail forward, Grant Access to a mailbox, manage Send As and Send on Behalf permission in Office 365

You would need Windows Power Shell to execute commands on Microsoft Office 365. Here are the steps once you have Windows Power Shell installed on your computer:

Connect to the Office 365 Server

$LiveCred = Get-Credential

Setup Session

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $LiveCred -Authentication Basic -AllowRedirection

Set Execution policy to run cmdlets

Set-ExecutionPolicy Unrestricted

Import the cmdlets allowed in the session

Import-PSSession $Session

Set mail forwarding

Set-Mailbox -Identity "<MailboxID>" -ForwardingSmtpAddress "<Target SMTP Address>" -DeliverToMailboxAndForward:$true

Verify mail forward

Get-Mailbox -Identity <MailboxID> | Select ForwardingSmtpAddress

Other Commands:

Grant Admin Access to a mailbox:

Add-MailboxPermission  <MailboxID> -User <AdminUserMailbox> -AccessRights FullAccess -InheritanceType All

Grant Send As permission on a mailbox:

Add-RecipientPermission <MailboxID> -AccessRights SendAs -Trustee <AdminUserMailbox> 

Verify Send As Permission:

Get-RecipientPermission -Trustee <AdminUserMailbox>

Grand Send On Behalf Permission:

Set-Mailbox -Identity <MailboxID> -GrantSendOnBehalfTo <AdminUserMailbox>