Try telnet from your PC to get the settings, it is most probable that it can reach the IP address (Assuming time/gateway/DNS is correct on the DocuPrint) but that the port you are using is not running a mailservice (25 is the default, but it could be 465 for SSL, 587 for TLS etc etc)
So via telnet in the Windows Command line you could find the settings of the server once you got it connected.
Obviously that won't help with authentication, but typically encryption is found in the 250 responses (SSL/TLS/STARTTLS)
I cannot give specifics here since I have no idea of what your mail server is running. Normally if someone provides an SMTP provider we can just look up the settings (Comcast/AOL/Gmail/Yahoo/Office365)