How do you keep HubSpot marketing email out of the spam folder?
Authenticate the domain, clean the list, warm the sending IP, and watch engagement.
In priority order: authenticate your sending domain, clean your list, warm the sending IP if you have a dedicated one, and then watch engagement. Subject line tricks are the last five percent and people always start there.
1. Authentication, before anything else
Connect your email sending domain in HubSpot and publish the DNS records it gives you. That means SPF, DKIM, and a DMARC record. Google and Yahoo's bulk sender requirements made DMARC a practical requirement for anyone sending volume, and an unauthenticated domain will get filtered no matter how good the content is. If you only do one thing from this article, do this one.
2. List hygiene
Mailbox providers judge you on how people react. Sending to an old list with dead addresses produces bounces and spam complaints, and that damages the reputation that decides where your next send lands. Run the list through a verification service before a first send to an aged database. Suppress hard bounces permanently. Stop mailing people who have not opened anything in a year, which feels like losing reach and is actually how you keep the inbox placement of everyone who does engage.
3. Volume and warming
New domain or new dedicated IP means you start small and ramp. Sending fifty thousand emails from a cold sending identity is the fastest way to a blocklist. Start with your most engaged contacts, because early positive engagement is what builds the reputation the larger sends will rely on. HubSpot's catalog documents Marketing Hub monthly send limits as a multiple of your marketing contact tier, currently 5x on Starter, 10x on Professional and 20x on Enterprise, which is generous enough that the constraint on volume should be your list quality, not your plan.
4. Then content
Once the first three are right, content matters at the margin. Avoid the obvious trigger language, keep a real text to image balance, include a genuine plain text version, and make the unsubscribe easy to find. A hidden unsubscribe link does not reduce unsubscribes, it converts them into spam complaints, which cost far more.
Deliverability is maintenance, not a project. Check bounce and complaint rates monthly.
Related: Email List Cleaning Best Practices, How to Warm Up a New IP Address, How to Keep Your Email IP Healthy, The Ultimate List of Subject Line Spam Triggers.