1234, Main Street
Boston, MA 02123
<Recipient Address Goes Here>
I thought I should let you know of a matter that may be of some concern to you. <hiring period> we hired <employee name>. Although <he/she> has been a very satisfactory member of the team here at Abc Company, some comments <he/she> has made recently are troubling and could cause problems.
It seems that <he/she> has been speaking very unkindly about your company to other employees, and possibly even to outside companies. While I respect my staff’s privacy, I also do not condone this sort of behavior. I am informing you of it because a brief letter or phone call on your behalf may curtail the negative comments before they cause damage or necessitate legal action. I’m sure you would do the same for us at <employee name> were our positions reversed. I have already taken action to ensure that <employee first name> knows that this kind of behavior will not be tolerated. Thank you for your time.
encl: <List of enclosed items goes here>