I receive shedloads of catalogues - a few I subscribe to and the majority I do not. I tried emailing the various companies asking them to take my name off their mailing list - consternation - I found that many of these companies then started sending me two catalogues!
A friend advised me the best way to stop these catalogues from flooding through your letterbox was to just scrawl 'Return to Sender' upon the outside and cover up your own name with a label requesting removal from mailing list and post back. This seemed to work for a bit - just a little bit.
I think our local sorting office decided I was a nuisance and I found the wretched catalogues returning to me with my sticky label torn off to re-display my name and address. I now have a different system - I add the return address on another sticky label - I think the sorting office do not like searching the catalogue for the return address - so far success.
We do not have a letter box - we have an American style mail box attached to our porch. All of the four new houses find these difficult. If we go away we have to arrange for a neighbour to empty our box - I think it can only hold about 5 thick A4 letters in total. You ask why do we not insert a letter box - we have very nice thick oak front doors - it would be a mammoth job to install a letter box - way beyond Husband and I.