Just wondering if I am beng over suspicious.

I have had a dvd rental company that send me dvd's. For the last 4 months it's been fine then this week one dvd has not appeared and the other one has been opened then resealed, (if you get rental dvd's through the post you will know what I mean!)

I'm really worried that is someone who lives in one of the four other flats has been 'borrowing' my dvd's (five flats share the same letter box) I can't imagine that it would be the postie, though you never know!

What should I do? Has anyone had this problem with neighbours 'borrowing' post, what happens if it is my bank card next? I don't really talk to the other people in the flats but two new people have moved in recently.

My other option is to somehow secure a locked post box to the outside of the house and ask the postie to post my flat number in the box instead? Would this be ok with the post office? and would it annoy the other flats if they think I'm that suspicious of them of nicking my post that I have to have my own box?