Site emails state incorrect domain name
Go to:


  admin>configuration>people>account settings


Scroll down and you will see 8 email options for account activities such as account activation, password recovery, etc..

The Default token inside these emails is [site:name] which I presume is what's giving you trouble? Or do you have it set to [site:url]? 

Regardless possible next steps:


Manually set the link location by adding something like this to the emails ... (kind of hacky)
"http://www.mywebsite.com"
Add HTML functionality to your emails... and then apply above solution with nice html link markup (still hacky)
Try setting a specific domain as your $base_url in sites/default/settings.php. This will disable the dynamic detection of your base domain...
Failing the above investigate further here:- Your Drupal Site Pretending to be Another.