This would be my response, and it would not be an e-mail. A copy would be sent registered mail and a copy sent regular mail (just in case he didn't go sign for the other).
Your name
Your address
His name
His address
Re: chickens
Date
cc: my attorney, local law enforcement
Dear Neighbor,
You and I have exchanged negative e-mails regarding my right to have chickens and your disapproval of the chickens. You have threatened poison and and attacked my character with a disgusting racial slur. I have decided to take the high ground and will no longer respond to your repulsive rants.
The zoning regulations do not prohibit keeping poultry on my property. I am sure that you are capable of looking up the appropriate zoning ordinances yourself so I will not include them here. My lawn is mowed regularly. I am not violating any local codes or ordinances.
You have indicated that you intend to place poisons near the fence/property line. Since my animals do not cross over to your property, they will be safe. However, if any of my animals suffer from poisoning, I will assume that you purposely or negligently placed poison on my side of the fence. Therefore, any poisoning of my animals will result in legal action against you. I thank you for putting your threats in writing. That makes documenting your threats and intentions much easier. I would also like to make you aware that there has been no evidence of rats on my property.
I would also like to bring to your attention that placing notes in other people's mailboxes is a violation of federal laws. Please keep this in mind if you feel the need to place less than helpful notes and suggestions in other people's mailboxes as I suspect you have done in the past. I, for one, will no longer tolerate such behaviour and will report it. I have spoken to others in the neighborhood and they are of like mind.
I fully intend to keep and maintain my poultry on my property in the manner in which I see fit. If you have the desire to live in an area that restricts animal ownership, I suggest that you move to such a neighborhood. I specifically chose to purchase my property because the zoning allows poultry. I did a great deal of research on the zoning regulations before moving here. I suggest that you do similar research the next time you buy a home.
Please do not send me any more e-mail correspondences. I will consider any further hostile communications from you as harrassment and forward them to my attorney and local law enforcement. We live in a civilized society and are a community of laws. I respect those laws, and I hope you will do the same. If you would like to communicate with me regarding this matter, I would suggest that you find a civilized manner to do so.
Best Regards,
X