How do I set up an Exchange Account in Mac Mail?
Domain shuld be the beginning part of your username when you logon to your machine or account at work.  It's the name of your internal corporate network.  It looks like this when you sign on to machines at work:

netbsa\myusername


You might need to specify this format as your username in mail.app.  However, if it's timing out, it's probably more likely that the server settings are wrong.  Don't use the https:// part in the server settings and see if it will connect.