How do I Send As another mailbox?

If you have access to a secondary mailbox (such as a resource account or shared mailbox) and you want to send emails from that other email address, you will additionally need Send As permission granted by CTD in order to send emails as that account.

Steps

Once Send As permission has been granted, you'll only need to do this set of steps once.

1. In a new email window, navigate to the Options tab. Click the From button - this toggles the visibility of the From dropdown option.
2. Click the arrow to the right of From, then select Other Email Addresses...
   
3. Instead of typing in the address, it's important to click From.... Another window will pop up. You'll want to select the Global Address List (GAL) from the dropdown, then search for the name of the secondary mailbox. Select it, then click OK, then click OK again.
   
4. Now you'll be able to select the secondary mailbox from the From dropdown menu in the future. 

Repeat these steps as necessary for other mailboxes.

Troubleshooting

If you are running into issues with Send As, the first step is to delete the cached entry from the From dropdown.

1. Click the arrow to the right of From.
2. Click the x to delete the existing From option.
   
3. To re-add it, repeat the steps in the above section.

Please note: You may need to delete the cached address every time you send from the secondary mailbox.