In Ireland, where I used to live they put down strychnine in the fields to kill dogs that stray. In Thailand they poison a barking dog if its annoying and an owner refuses to do anything. I lost two dogs that way, not because I refused to do anything, but because I was away and someone did not do their job. There are more drastic actions than pushing a note through the letterbox. I remember how the central character dealt with a dog, a true story in, ‘I walked by Night’ an autobiography and a quite rare book too. Don’t read it unless you are a psychopath. Personally a sedative stuffed in a sausage would be preferable to poisoning. You can complain anonymously, you don’t have to give your name, you can say the dog barks because its mistreated. If it was a choice of my sanity or the dog the dog would have to go. I once may have run my hosepipe into a neighbours garden on a night it chucked it down. Left it on about 6 hrs. The garden became a sea of mud that lasted for days and ruined the lawn. Nobody puts a dog out if its going to be covered in mud. It also makes a good case for complaining about the poor conditions the dog is housed in. Some people would give the dog the trots and see how soon they get rid of it. Another thing someone can do is tempt the dog to go for a ride and take it about 100 miles away minus collar and leave it in a retirement community. They would soon give it scraps and it would be someones else’s problem. I could not, of course suggest anyone follows any of the suggestions above. Neither would I ever suggest I had done any of the above. Neither would I say I have not. Just some observations on what someone driven to distraction might do. The kindest is rehoming.