1) Select Tools -> Account Settings. Select Account Actions (at the bottom) -> Add Mail Account …
2) Specify your name, email address and the password for your email address, then click Continue. Thunderbird will try to guess the server settings for your account.
4) Select IMAP or POP3 from the Incoming server drop down.
Specify the Incoming mail settings: mail.mrhost.ca, port 110, SSL none (or STARTTLS) and Normal Password Authentication.
Specify the Outgoing mail settings: smtp.mrhost.ca, port 587, SSL none (or STARTTLS) and Normal Password Authentication.
Username should be your full e-mail address.
5) Select Create Account.