This article describes the steps for retrieving a required server certificate when your FTP application requires TLS or SSL protocols. This is applicable to FTPS, not to be confused with SSH FTP (SFTP).
1. Using OpenSSL from a command prompt, execute the following command for against the FTP server (replace ftp.xxxx.at with your FTP host):
openssl s_client -connect ftp.xxxx.at:21 -starttls ftp
2. Copy and save the certificate (between and including the lines below) into a new text document with a (.cer) extension.
3. Import the certificate as described here: Creating a certificate by importing a certificate