Hello, Unfortunately, there is no way to disable the unsubscribe option for mailing list subscribers. The FTC requires that you tell your recipients how they can unsubscribe from future emails.
Tell recipients how to opt out of receiving future marketing email from you. Your message must include a clear and conspicuous explanation of how the recipient can opt out of getting marketing email from you in the future. Craft the notice in a way that’s easy for an ordinary person to recognize, read, and understand. Creative use of type size, color, and location can improve clarity. Give a return email address or another easy Internet-based way to allow people to communicate their choice to you. You may create a menu to allow a recipient to opt out of certain types of messages, but you must include the option to stop all marketing messages from you. Make sure your spam filter doesn’t block these opt-out requests.
For more information on this, you can look up the CAN-SPAM Act which covers this.
I hope this helps.
Dylan Kwan
System/Network Administrator
SmarterTools Inc.
www.smartertools.com