Steps:
Login to outlook.com to enable POP3 mail downloads
Click on Settings and then More mail settings
Select Connect devices and apps with POP
Select Enable and click on SAVE
Now open Thunderbird and select File->New->Existing Mail Account
Fill in your Name, Email address and Password and click on Continue
Set the following settings to the details below: INCOMING: POP3**
Server hostname**: pop-mail.outlook.com Port: 995 SSL: SSL/TLS Authentication: Normal password
**OUTGOING: SMTP
Server hostname**: smtp-mail.outlook.com Port: 587 SSL: STARTTLS Authentication: Normal password
Click on Done