Keywords: Office 365, Oultook Send As, Force Global Address List (GAL) update, This message could not be sent
1 Configure Send As permission in Microsoft Exchange
1.1 Login to Office 365 Exchange: https://outlook.office365.com/ecp
1.2 Click on “recipients” -> “mailboxes” or “shared”
1.3 Double click on one of the mailbox from the results list
1.4 Click on “mailbox delegation”
1.5 Scroll to “Send As” section
1.6 Click on “+” button, add user who should have Send As permission for the mailbox.
1.7 Click on “Save” button.
2 Send As from Outlook Online
2.1 Login to https://outlook.office365.com as the user we have specified in step 1.6
2.2 Click on your profile image at top right corner
2.3 Click on “Open another mailbox”
2.4 Enter the mailbox we give permission to from step 1.3 and click on “Open”
2.5 Now you can send email from this email address.
3 Send As from Microsoft Outlook Desktop Application
3.1 Launch Desktop Outlook
3.2 Click on “New Email” button
3.3 Click on “Options” from Menu then click on “From”
3.4 Click on From, if the address you want to send as appear underneath the “From” button, select it, if not, Click on “Other Email Address…”
3.5 Type the email address you have configured from step 1.3
3.6 Now you can send email from this email address.
4 How to resolve following Error
Note: You may encounter following error after step 3.6
This message could not be sent. You do not have the permission to send the message on behalf of the specified user.
To resolve this issue, try following method to Force Oultook update Global Address List (GAL) to resolved the issue.
4.1 Make sure the Desktop Outlook is closed
4.2 Open following path from Windows File Explorer
%userprofile%\AppData\Local\Microsoft\Outlook\Offline Address Books\
4.3 Cut everything within this folder
4.4 Create a new folder name it backup and open it
4.5 Paste to the backup folder
4.6 Try to launch Desktop Outlook and follow Section 3 again to Send As, this time there should be no error.