For these instructions, I'm using Linux Mint 14 XFCE.
Click on Menu / Internet / Thunderbird Mail

Your name:

Type in the name you'd like to appear on your emails.

Email address:

Type in your email address.

Password:

Type in the password for your email address.
Select Remember password.
Click the Continue button.

It'll try to automagically configure the settings,
but it never gets it right, so click the Manual config button.

Incoming:

POP3

Server hostname:

mail.glis.net

Port:

110

SSL:

None

Authentication:

Normal password

Outgoing:

IMAP

Server hostname:

mail.glis.net

Port:

587

SSL:

None

Authentication:

Normal password

Username:

username@glis.net

Click the Done button.

This warning states your not using a secure mail server. Mozilla Thunderbird explains it here.
Why does Thunderbird warn me that my server doesn't use encryption?

To continue creating the account you can place a check mark next to I understand the risks.
Click the Done button.