The employee needs to be polite, and they can show this by using polite phrases such as “Thank you for contacting me”, “Thank you for reaching out to me” and a few more which can be found further down in the article. It doesn’t matter if the customer is contacting you with good intentions, a specific query, or a complaint.
It is a polite greeting to the customer by which they want to show that any inquiry is welcome.
The phrase “Thank you for contacting me” is most commonly used in co-ops by employees who work with customers.