Is it true Brazil customs screen ALL foreign mail (including letters)?

Hi, a friend posted an envelope from London to where I live in South Minas Gerais (approx 2 hours north of Sao Paulo on the border of MG and SP) about 2 weeks ago. The envelope contained some post I had redirected (bank statements, new debit card, etc.) from my old address in London. It was sent first class with no tracking number and cost about �3.50. He was told by Royal Mail it should take 10 days at most. The envelope weighed about 120g. I have been reading Brazil customs screen everything sent from overseas and it might take at least a month. Is this correct or does this only apply to packages, etc so they can apply customs duty? Thanks for your help.