Petfavors.com typically provides a straightforward way for customers to unsubscribe from their mailing list. Usually, at the bottom of each email that you receive from them, there is an unsubscribe link. By clicking this link, you should be guided through a process to remove your email from the list.
Alternatively, you may find an option within your account settings on their website if you have an account. It is always a good idea to check the current web page for detailed instructions, as the process may vary slightly over time. If you encounter any difficulties, the website may also have a help or FAQ section that can furnish you with additional guidance.