This letter informs a company about a potentially libelous or slanderous piece of information that you have seen.
1234, Main Street
Boston, MA 02123
31 March, 2005
<Recipient Address Goes Here>
I have been a customer of <company name> for <time you've been a customer>. Because I like your company and the <products/services> you provide, I feel it's my duty to inform you about potential <libel/slander> against <company name>.
I thought I should inform you of this matter, since you have treated me with nothing but courtesy and professionalism. If you wish to pursue this matter and need more information, feel free to contact me.
encl: <List of enclosed items goes here>