Firefox isn't your email client and thunderbird doesn't have an easy GUI way to do this, but it can be done.
Thunderbird does not provide a way of changing the POP3 timeout in the GUI. You need to create a user preference override.
You can do this by creating (or adding to) a file called user.js in your Thunderbird profile folder. Use your text editor of choice, notepad, etc.
To change the POP3 timeout add the lines:
// Increase pop3 timeout:
user_pref("mail.pop3_response_timeout", 120);
In this example the timeout is set to 120 seconds (instead of the default 45 seconds of Thunderbird). Adjust the time as you need.