Today, I got a call from the agent telling me to "stop spamming my clients, it's not an open listing".

@Steve Yang  Sorry for the delay....my alerts are going to spam.  

If you send to many email correspondence to people that don't want them then they'll mark you as SPAM.

That would classify as SPAM so its not something you could legally do.

I am getting a barrage of spam requests on VRBO. 

So sorry, didn’t mean to spam.

The rules for engagement have been clearly stated, and anyone who spams  you loses their messaging privileges.

If you haven't seen an email from me (check your spam folder too), email me and let me know.

Every homeowner is bombarded with "we buy your house" junk mails, text messages, spam phone calls every day, so how are you differentiate yourself from a million other wholesalers in the market?

This isn't a spam post, I was a real estate investor for decades and I am currently retired and do other "out of the box" investments.