The mother-of-two said the prank was "potentially dangerous" if it was sent to someone in a volatile relationship.
"The fact that someone is going out making these accusations where you can only go on someone's word [to prove it's not true] ... my husband knows me well enough and trusts me but it is a horrible situation," she said.
"People need to be aware that just because someone puts something like this in your letterbox, you shouldn't believe it."
Her neighbour, Mary Fakalata, received an identical note, which left her feeling upset and scared.
"I was standing in the kitchen trying to work out what's going on. I thought maybe a friend was playing a prank so I checked again and there was no sender," she said.
"After I studied it again I put it in the rubbish ... it was very upsetting, so scary. I thought maybe someone had been watching me all day although I know for sure it's not true. I couldn't do anything yesterday, I was just so lost."
Fakalata said her husband suggested it might be from someone trying to split them up.
Counties Manukau Police spokeswoman Kimberley Mathews said if people were receiving these notes and were concerned for their safety they should report it to police.
"Police urge anyone engaging in this type of behaviour to consider the consequences of their actions," she said.