Reworded the last sentence because I felt the old one was a bit combative instead of constructive. I also tried to individually cover the three classes of scenarios I've encountered in which I might have used such a response: "Why doesn't my Windows work?", "apt-get works on only half my servers" (turns out the other half are RH/CentOS), and "The following is an exhaustive dump of every problem I've had on any of my servers in the last fortnight. <snip>thirty-page text dump</snip> How can I fix it?"

And here I thought, "Wow, there are enough people having issues with cal(1) that they've submitted 15 questions on it? It only has six options!"

As a professional sysadmin who despises CPanel, I think this answer is getting unnecessarily dogpiled. Just because I use qmail and bash on Linux, and you use sendmail and tcsh on AIX, does not mean that I can't try to help you solve your problem. I won't be able to tell you what to type, but I can certainly tell you to "check whether you can connect to the machine on port 25" and you can interpret that accordingly and implement the test. If you can't, then either it's a CPanel limitation or you're not professional. In either event, the question should (only then) be closed.