How to reinstate the POP folder in 'outlook.com' mail?

Outlook.com does not use a separate POP folder. POP is an access method for downloading mail, not a folder in Outlook.com.

If POP access needs to be turned back on in Outlook.com:

1. Open Settings.
2. Go to Mail > Forwarding and IMAP.
3. Under POP and IMAP, turn Let devices and apps use POP to ON.
4. Select Save.

If the goal is to use Outlook.com with a mail app that connects by POP, these are the supported POP settings:

• POP server: outlook.office365.com
• Port: 995
• Encryption: SSL/TLS
• Authentication: OAuth2/Modern Auth

For sending mail:

• SMTP server: smtp-mail.outlook.com
• Port: 587
• Encryption: STARTTLS
• Authentication: OAuth2/Modern Auth

POP and IMAP access are disabled by default in Outlook.com, so re-enabling POP in Forwarding and IMAP is the required step.

References:

• POP, IMAP, and SMTP settings for Outlook.com | Microsoft Support