Addon domain is redirected to the main domain

Question

I have a hosting service with two addon domains.

Everything worked well until a few weeks ago.

If I go to www.addon1.com, it redirects to www.mainwebsite.com. The same thing happens for www.addon2.com.

But if I go to www.addon1.com/index.php, it loads correctly.

I really don't know what the problem is.

Is there anything I can do (htaccess or something else) to ensure that www.addon1.com is not redirected to www.mainwebsite.com

EDIT

Contents www.addon1.com.htaccess

Options -Indexes

Content www.mainwebsite.com.htaccess

Options -Indexes
Redirect 301 /index.html http://www.mainwebsite.com/index.php
Redirect 301 /portfolio.html http://www.mainwebsite.com/portfolio/index.php
Redirect 301 /services.html http://www.mainwebsite.com/services/index.php

Answer 1

"" , , ( - www.addon1.com).

www.mainwebsite.com .htaccess :

    RewriteCond %{HTTP_HOST} ^(www\.)?addon1\.com
    RewriteRule .* - [L]
...

* [L] .

mod_rewrite, , - addon1.com www.addon1.com.

, -: http://htaccess.madewithlove.be/ .

1- : www.addon1.com

: , , !

: www.whatever.com

. !

, , , , ! , .htaccess

, !

Answer 2

.htaccess 301:

RedirectMatch 301 /(.*)   http://www.mainsite.de/index.php

, , .