Thunderbird Setup

Use Edit → Account Settings ... to configure your e-mail account(s)

Fill in reasonable settings ... compare with mine below.

Bart.Swennen@imap2 - Server Settings - Copies & Folders - Composition & Addressing - Offline & Disk Space - OpenPGP Security - Return Receipts - Security Local Folders - Disk Space Outgoing Server (SMTP)
Add Account...
Set as Default
Remove Account