I am a moderator at Drupal answers, and migrated this question to SF a few days ago. I migrated it because it didn't really have anything to do with Drupal or Drupal configuration. It is essentially about getting Plesk to map different domains to the same directory, each with their own IP address.
What in particular about this is off-topic? Is Plesk considered a non-professional environment, and therefore off-topic?
Web site control panels such as cPanel and Plesk are extremely unlikely to be used in a professional environment. They're more commonly seen with small and one-man operations where the expense of the control panel is judged to be less than the expense of an actual system administrator.
While the control panels make it relatively easy for users to perform basic administration tasks, the main disadvantage is that they tend to take over the systems in strange and non-standard ways, making it difficult or even impossible for actual system administrators to manage the servers normally. Since there usually isn't a system administrator, the problem often goes unnoticed...
Until you bring such a question here.
So things that fall outside the norm, or the feature set provided by the control panel, can't be done easily (or at all) while they would be easy or trivial with a sysadmin running the machine in the usual manner. The question you referenced falls into this category.
The main problem, then, from a system administrator perspective, is that these systems are virtually unsupportable. For nearly any question, including the one you referenced, my response would have to be "Wipe the system and set it up right this time, without the control panel. And hire a sysadmin while you're at it." Obviously, this is not helpful in the short term, but there's little more we could possibly do, other than closing the questions as off topic.
See also the related question, Are cpanel questions really 'professional sysadmin' related?
For what it's worth, I would have voted to close that as NARQ or NC, rather than off-topic.
The question doesn't really have enough to go on (as mentioned by the porcupine, a lot of that is the fault of the control panel), and is basically unanswerable as is. So even if not off topic, it's still not really a question that can be answered, at least not in a useful way. ("RTFM, FFS" not being a very useful answer.)
