The letter "pretends or looks like the official notification from the registrar of the domain names", when in reality the letter is just a "courtesy" reminder. They are able to know all your public information if your domain name registration is not private. (see Who Is for more information).
Please, under any circumstances DO NOT SEND ANY PAYMENTS TO THIS COMPANY. They are not in any way entitled to renew your domain unless you switching the registration of your domains with them, and sending a payment will not initiate any domain transfer process.
BE CAREFUL. Not only will they try to take your money, they will also try to get authority over your domain by asking you to transfer the domains to them, which will result in a more expensive service, they will charge you almost 3 times the regular domain renewal price ($15 vs $40 per year).