Can I include marketing content in transactional emails?

You can, but there's a real line you don't want to cross. The short answer is yes, a little marketing content in a transactional email is fine. The longer answer is that once the marketing content becomes the main event, you've turned a transactional email into a marketing one, and that changes everything legally and deliverability-wise.

Under CAN-SPAM, the rule is called the primary purpose test. It asks a simple question: would a reasonable person open this email and think it's mainly about the transaction, or mainly about selling something? If the answer tilts toward selling, your email loses its transactional exemptions. That means you'd need an unsubscribe link, a physical mailing address, and all the other requirements that apply to marketing email. Miss those and you're looking at a compliance problem, not just a deliverability one.

Here's what actually passes the test and what doesn't.

Generally fine to include:

• A small "you might also like" product row below an order confirmation (the order details are clearly the point of the email)
• A one-line referral mention in the footer of a shipping notification
• Social media icons in the footer
• A brief "thank you for being a subscriber" note in a receipt

Where it gets risky:

• A subject line like "Your order is confirmed + 20% off your next purchase" pulls the email toward marketing territory even before it's opened
• More than roughly a third of the visible email being promotional content
• Putting a sale or offer above or before the actual transactional content
• Sending what is essentially a promotional email with a thin transactional hook attached ("Your account is active, now check out our new plans")

The practical rule is simple: transactional content goes first, stays primary, and any marketing sits clearly below it. If someone skims your email and can't immediately tell it's a receipt or a password reset or a shipping update, you've gone too far.

There's also a deliverability argument beyond the legal one. People open transactional emails at very high rates because they expect something useful. If they start associating your order confirmations with promotional pitches, complaints go up, engagement goes down, and eventually those high-performing emails stop performing. The trust is the asset. Don't trade it for a banner ad.

Now if you're not sure where your email lands, our free Email Header Analyzer can help you look at how the email is being classified. Or if the question is more strategic, the SOS hotline is a free call, no pitch.