Yes. They`re seeing exactly what they should. Effectively what you are doing is sending the message to yourself (You get a copy) and the "blindcopies" (Your distribution list) also get copies BUT they don`t get to see who else is on the distribution list. If you put that list in the "cc" box everyone would see the recipients and be able, for example, to copy it, steal the addresses etc. Not only that there could be a very long list of recipients at the top of the e-mail which is a bit of a pain if you print it out.