I have a problem with the opening "To whom it may concern". This is the sort of opening you would use in message in a bottle type scenario. You have no idea at all who will find the bottle so the only alternatives would be something like "Dear Bottle Finder".
In almost all cases something is known about the recipient. Even if you dont have a name you can address it to the office or position of the person. eg
The Manager
MakesUPuke Pizza Parlor
Main Street
Dear Sir,
...
If you want to address a department, where you dont know, or care, who will open it, then use "Dear Sirs,"
NeverPaysOut Insurance
NotOurFault House
Main Street
Dear Sirs,
...