There are secure ways to run things and insecure ways to run things. It's very possible to setup a postfix or exim smtp server as an insecure open relay running on port 25. It's also possible to have either running securely on port 25... And an open port is meaningless by itself. It's the security options applied by the system and application running a service on the port that matter.
The examples you give are just applications that run over http or https... https requires an SSL cert from a trusted CA, and http is a very bad idea for anything that you log into, or that has free access to your home network from the Internet.
I imagine most users skip this step... http://docs.qnap.com/nas/4.0/en/security.htm?zoom_highlights...
Note, the SSL certificate instructions... You can upload a secure certificate issued by a trusted provider. After uploading a secure certificate, users can connect to the administration interface of the NAS by SSL connection and there will not be any alert or error message.
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The error message referred to here is the web browser message indicating that the SSL certificate doesn't match a trusted CA, and therefore your "secure" NAS connection might be Man-In-The-Middle attacked... And if you don't upload an SSL cert - and connect via http externally - it means that the most amateur of "bad guys" already has your 30 character username and your 45 digit/character/special character password...