This is standard and understandable reason for unsubscribe, only effecting your exact email subscription that has been sent.
As with option 1, if your client no longer wants to hear from a specific Realtor this will stop all emails from you.
This is where the problem arises, if other Realtors have previously set up saved searches and the prospect has unsubscribed by using option 3 you will not be able to message the prospect until they 'resubscribe'.
If you'd like to learn more about the CAN-SPAM Act use this link
By leveraging your own website that uses an IDX feed you can send out similar emails, allow access to saved searches for your clients, and have complete control over who can get what. In addition, providing yourself additional opportunities to brand yourself, your team, or your brokerage so that you stand out from your competition. A dynamic real estate website design can not only do many of the features that you need during your normal day-to-day, but it can also attract new buyers and sellers by providing a consistent marketing message.
Have you run into this problem with your MLS system? If so, please let us know in the comments. If you have some helpful resources for SWFL Realtors to use if this issue arises please let us know in the comments also.