Every contact has a marketing contact status property. Contacts set as marketing can receive marketing emails and be included in ad audiences from HubSpot. Contacts set as non-marketing remain fully usable for sales and service: reps can still email them one to one, log calls and associate them with deals and tickets. Your HubSpot subscription counts marketing contacts, so the number matters to your plan as well as to your sending.
Contacts can be set as marketing by hand, in bulk, through workflows, during import, or when they are created by forms and integrations, depending on how each source is configured. Setting a contact back to non-marketing may not take effect until your next billing update date, so check the timing in your account before a large change.
Marketing contact status is not the same as consent or subscription status. A marketing contact can still be unsubscribed from every email type, and in that case they will not receive your emails. Who you are allowed to email, and on what legal basis, is a separate decision for a responsible person in your company. This page is not legal advice.
Teams that manage marketing contacts well set clear rules for who should be marketing: for example, contacts with a valid email who are subscribed to at least one email type and have engaged in the last year. They use an active segment to find contacts that should be non-marketing, such as bounced, unsubscribed or long-inactive contacts, and review it on a schedule rather than letting every new record default to marketing.
Example
Pinecrest Outdoor, a fictional retailer, found that 30% of its marketing contacts had hard bounced or had not opened an email in two years. The marketing lead reviewed the segment, agreed the rule with the person responsible for email compliance, and set those contacts as non-marketing. Sends got smaller, and open rates became a truer measure of engagement.