Error 550 Permission denied: Windows Server 7 FTP Server ?

The 550 Permission denied error on a Windows 7 FTP server usually means the user does not have permission to access the FTP folder from outside (Internet), even though it works on the LAN.

This typically happens due to folder permissions, IIS FTP authorization, or firewall/NAT issues.

Checklist to fix it:

1. NTFS Folder Permissions

   • Right-click FTP root folder ? Properties ? Security

   • Add the FTP user (or IUSR)

   • Give Read / Write / Modify permissions

2. IIS FTP Authorization Rules

   • Open IIS Manager

   • Select your FTP site ? FTP Authorization Rules

   • Add rule ? Allow ? Specific user or All users

   • Grant Read / Write

3. Windows Firewall

   • Allow FTP Server (FTP Traffic-In)

   • Ensure port 21 is open

   • If using Passive FTP, open the passive port range

4. Router / NAT Port Forwarding

   • Forward port 21 to the local IP of your FTP server

   • Forward the passive FTP port range as well

5. FTP User Isolation (if enabled)

   • Ensure the user’s home directory exists and matches IIS settings

Why it works on LAN but not Internet
LAN bypasses NAT and firewall rules. From the Internet, blocked ports or missing permissions cause the 550 error.

Once permissions + firewall + port forwarding are correctly configured, the error will be resolved.