Note on your screen, you should have mail.<yourdomain.com> and not mail.lcrcomputer.com.
The important thing to note on this screen is that the Outgoing Server will use Port 587 and Secure Connection is set to None.
Please note: You can set Thunderbird to Leave messages on the server. Just remember that Thunderbird can get confused and think all messages on the server are new and re-download them, creating duplicates.
Also Thunderbird defaults to checking email every 10 minutes. While we have not had reports of this happening with Thunderbird, setting this option to less than 10 minutes has been known to cause duplicate emails in your Inbox. We will ask how often you check for new email and we will advise you to set this to at least 10 minutes before taking any further action on such reports.