Yes, the sentence is grammatically correct. It conveys a request for someone to refrain from engaging in sexual relationships with their neighbor, even though the speaker is unclear about the intended audience of the message.
Here are a few possible rephrasings:
1. "I'm not sure who this message is intended for, but please refrain from having sexual relationships with your neighbor. Thank you."
2. "I don’t know who will read this, but I


