How to fix FileZilla's response: "550 The supplied message is incomplete. The signature was not verified."?

Question

How to fix FileZilla's response:

550 The supplied message is incomplete. The signature was not verified.

What is wrong with this? Is this in my hosting site or in my FileZilla setup?

Answer 1

If the patch @Martin mentioned (KB 2888853) doesn't solve the issue, try the suggestions below.

If you get “This update is not applicable” error while trying to install the hot-fix:

1. Extract the KB (MSU file) using the below command.

   Expand –F:* [path of downloaded KB] [Destination folder where you need to extract]

2. Run the below command to install the patch on the currently running system:

   DISM.exe /Online /Add-Package /PackagePath:[path of the extracted file (select.cab file)]

Try connecting to FTP server via IP

If you are using a hostname such as ftp.domain.com to connect to FTP, perform the following instructions:

1. In your client machine, open hosts file (C:\Windows\System32\drivers\etc\hosts) Enter the line below and save it (Enter your IIS server’s IP address instead of 192.168.1.100)

   192.168.1.100 ftp.domain.com

2. In command prompt, run ipconfig /flushdns

Try to connect to FTP server again. If it doesn’t work, continue with the next sub-section below. If it works, it means there is a firewall blocking the FTPS port between client and server

Try using SFTP instead of FTPS

FTPS uses two channels: Command Channel and Data Channel. Some firewalls and routers allow Data Channel communication after reading the Command Channel data. If they can’t decrypt the Command Channel data when FTPS is used, they may block Data Channel communication.

SFTP uses only one channel. Therefore, this issue may not occur if you use SFTP.

Source: (Solved) 550 supply message incomplete, signature was not verified

Answer 2

This error is returned by Windows IIS server due to a known bug.

For details see Microsoft article FIX: "The supplied message is incomplete" error when you use an FTPS client to upload a file in Windows.

Quote from my article about the bug.