I also get the "550 The supplied message is incomplete. The signature was not verified." error with version 3.7.0.2, using explicit FTP over TLS.
The connection does established, but if you want to upload any file, the above error appears.
Server 2012 / IIS 8 / With passive mode
@botg, if you need a test account for troubleshooting / reproducing, please contact me
Code:
Status: Starting upload of C:\temp\test.exe
Status: Retrieving directory listing...
Command: PASV
Response: 227 Entering Passive Mode (1,2,3,4,19,233).
Command: LIST
Response: 150 Opening BINARY mode data connection.
Response: 226 Transfer complete.
Command: PASV
Response: 227 Entering Passive Mode (1,2,3,4,19,234).
Command: STOR test.exe
Response: 150 Opening BINARY mode data connection.
Response: 550 The supplied message is incomplete. The signature was not verified.
Error: File transfer failed after transferring 1'225'748 bytes in 4 seconds
Status: Retrieving directory listing...
Command: PASV
Response: 227 Entering Passive Mode (1,2,3,4,19,233).
Command: LIST
Response: 150 Opening BINARY mode data connection.
Response: 226 Transfer complete.
Command: PASV
Response: 227 Entering Passive Mode (1,2,3,4,19,234).
Command: STOR test.exe
Response: 150 Opening BINARY mode data connection.
Response: 550 The supplied message is incomplete. The signature was not verified.
Error: File transfer failed after transferring 1'225'748 bytes in 4 seconds
The connection does established, but if you want to upload any file, the above error appears.
Server 2012 / IIS 8 / With passive mode
@botg, if you need a test account for troubleshooting / reproducing, please contact me
