FluentFTP: The remote certificate is invalid according to the validation procedure

Question

When I try to connect to my FTP server to upload a file with FluentFTP I get this: The remote certificate is invalid according to the validation procedure. Yet FileZilla works fine with no error or warnings. Am I doing something wrong and if it's actually a problem with the server how can I ignore this error Here's my code: ``` var credentials = new NetworkCredential(Username, Password); FtpClient client = new FtpClient(Host, credentials) { Port = Port, EncryptionMode = FtpEncryptionMode.Explicit }; client.DataConnectionEncryption = true; client.Connect(); var result = client.UploadFileAsync(FilePathName, RemotePathName, AllowOverwrite ? FtpExists.Overwrite : FtpExists.Skip, CreateRemoteDirectory, token).GetAwaiter().GetResult(); client.Disconnect(); ``` I also tried adding the event `client.ValidateCertificate += Client_ValidateCertificate;` ``` private static void Client_ValidateCertificate(FtpClient control, FtpSslValidationEventArgs e) { e.PolicyErrors = SslPolicyErrors.None; } ``…

Accepted Answer

`Client_ValidateCertificate` needs to manually accept the certificate like this:

```
private static void Client_ValidateCertificate(FtpClient control, FtpSslValidationEventArgs e)
{
    e.Accept = true;
}
```

However it's really a bad idea to just blindly accept any Certificate. I ended up doing something like this:

```
private void Client_ValidateCertificate(FtpClient control, FtpSslValidationEventArgs e)
{
    if (e.PolicyErrors == SslPolicyErrors.None || e.Certificate.GetRawCertDataString() == TrustedRawCertData)
    {
        e.Accept = true;
    }
    else
    {
        throw new Exception($"{e.PolicyErrors}{Environment.NewLine}{GetCertificateDetails(e.Certificate)}");
    }
}
```

FluentFTP: The remote certificate is invalid according to the validation procedure

Solution

Problem