Till now we were using only Webmail in Zimbra. Now some of our users wanted to use Outlook+POP3. While we were testing , I found one thing .
In new message window of outlook , users are able to insert the "From" tab and able to send from email@example.com.
For example: firstname.lastname@example.org is able to send mails from email@example.com or firstname.lastname@example.org using outlook. It is delivered to the recipient, saying that email@example.com on behalf of firstname.lastname@example.org.
Please tell me how can I block this from Zimbra.