Tracking the actions of non-leads
Right now we are setting up a campaign that sends out an alert to a homebuyer's real estate agent (the homebuyer is the lead, the real estate agent is an email address field we created on the buyer's lead card called 'realtor_email') when they reach a certain part of their homebuying journey. Seeing as a single real estate agent may be attached to multiple buyers in our system, we want to limit the number of times that the email address in the field realtor_email can be sent this particular message (essentially once per 6 months).
We currently do not want to make the addresses in realtor_email individual leads, as we already have too many leads in our system (these agents are contacts in CRM however).
This is the sort of logic we want to set up:
"if {{lead.realtor_email}} was sent alert (x) in last 6 months, do nothing"
Is there anyway to track whether or not the email addresses in 'realtor_email' were sent an alert, and reference those emails in a smart list (without creating new leads for the agents)?