Как изменить / удалить страницу веб-сайта cPanel по умолчанию для mail.domain.com?

Connect via FTP to your website, go to the document root, and create, or edit, the file called .htaccess. Your document root should contain either index.php or index.html file. That's how you know it's the document root. If the file exists, edit it. Otherwise, create it.

Now, edit that file, and make sure you have the following content. Some lines may already be there. Add this content at the end. If it already contains RewriteEngine On - dont touch it and just add the next 2 out of 3 lines below:

RewriteEngine On RewriteCond % ^mail\..*$ [NC] RewriteRule ^.* - [F] 

The first line enables the RewriteEngine. The second line specifies that the RewriteRule will work only if the domain starts with mail.. The final line, takes any request, and sends the 403 - Forbidden HTTP status message.

This should work fine if the server used is Apache HTTPD, however if others, like nginX are used, you'd have to look how to do the same with them. For nginX, it would be something like this:

if ($host ~* ^mail\..*$ ) { return 444; } 

Sending a non-standard, 444 status, causes the connection to close, without sending any response. Alternatively you could send 403 if you want a "Forbidden" status.

Unfortunately I can't vouch for nginX since I've never used it. Maybe you'd need to write that to a different file or something. I don't know. But you probably have Apache HTTPD there.

Also, this question belongs on either stackoverflow.com, or serverfault.com.

I am under the impression that the behavior of the default http response for "mail." + your domain is specific to the hosting company -- it's up to each company to configure it on their own, and different companies handle it differently. So if your hosting company tells you that that's not user configurable on their system, they may well be right. (Admittedly, there are other things hosting companies have told me weren't user configurable, which I figure out how to configure, but....)

I just checked some of my domains and others that I know the hosting companies of. Some are configured to redirect to "www.", others to the hosting company's own main page!

If this is sufficiently important to you, you may be stuck trying to talk the hosting company into making a company-wide change (which... not impossible, their present solution is unprofessional looking and redirecting to "www." would be nicer all around) or moving your business elsewhere.