My dad once wrote a letter to some government agency and when the responded they included a copy of the letter which started off with Dead Sir.

One of our customers at a University Dept of Anesthesia sent our statement back with a letter (btw the statement was about an overdue invoice for $620 and had columns Current over 30, over 60 so we highlighted the date the amount and the over 60) The secretary wrote that Dr. So&so of the dept of anesthesia received the statement but had no idea what it was for and if we could send a copy of the invoice. Then she (in a snotty manner) added "by the way, for your information Dr. Soso was born in 1941 so is not over 60. Cheers. PEtr