In 2010 you can add the “From: “ option in the settings. Problem solved if you have the permissions as listed below.
In 2007 (exchange) things run differently. You have to log into the server and give yourself send-as and full access permission in the exchange management console. Just right click the user mailbox and it should be in there.
After a certain mystery period of time, the changes will take place. It can be several hours in some cases and I thought it didn’t work up until it suddenly began working.
Next, log into OWA using IE which is usually at https://mail.domain.com/owa. Log in as your main user. On the top right you should be able to click your name and then enter another mailbox. Type the name you want, such as “bmurray” and then click Open.
It should open in a new tab and show you that mailbox. Any replying or sending from here will be from that mailbox. Test sending mail and if you get a permissions error then it could be that it needs more time or you need to add yourself under send-as in the server.
Useful commands that may also need to be run: (I ran these first and it did not work, but it could have been delayed so I’m not sure which part of this is necessary)
Get-mailboxserver <servername> | add-adpermission –user <service account> -accessrights GenericRead, GenericWrite -extendedrights Send-As, Receive-As, ms-Exch-Store-Admin
Note: <service account> is your user and doesn’t need the <>. Same with <servername>.
Add-MailboxPermission -identity “user” -user “serviceaccount” -AccessRights FullAccess
Note: ‘serviceaccount’ is the person who wants permission on the mailbox for ‘user’