IMAP

In the field marked Your name, type your name as you would like it to appear in your emails.

In the field marked Email address, enter your Videotron email address in lower case and without accents.

In the field marked Password, enter your password.

Check Remember password

After a search, Thunderbird will configure itself.

Click Manual config

Incoming
Enter 993 as port and select SSL/TLS as value of SSL.

Outgoing
Enter 465 as port and select SSL/TLS as value of SSL.

Click Done