Why your promo emails land in spam (and how to fix it)
The technical and behavioral reasons promo emails end up in spam folders, and the concrete fixes, from SPF and DKIM to list hygiene, that get them back into the inbox.
A promo email that never reaches the inbox does nothing, no matter how good the track is. Deliverability is mostly invisible until it breaks, and by then you've usually already sent a few campaigns into folders nobody checks.
The technical baseline: SPF, DKIM, and DMARC
These three records, set on your sending domain, tell inbox providers that your emails are actually authorized to come from your domain instead of being spoofed. Without them, providers like Gmail and Outlook have no reason to trust the sender, and trust is most of what deliverability is. If you're sending from a domain that's never configured these, fixing that is step one, before anything about subject lines or send times.
Engagement is the real ranking signal
Inbox providers watch how recipients treat your email: opened and read, opened and deleted, marked as spam, never opened at all. A list full of contacts who haven't engaged in months drags your sender reputation down for every email you send after, including to people who do want to hear from you. This is why pruning a stale list usually improves results even though it makes the list smaller.
What actually trips spam filters
Modern spam filters are less about "banned words" than about pattern-matching against known spam behavior: an email that's mostly one big image with almost no text, a subject line in all caps or full of exclamation points, a huge attachment instead of a streaming link. A short, plain-text-forward email with one clear link converts better and delivers better than a heavily designed one.
Warm up before you scale
A brand-new sending domain that suddenly blasts thousands of emails looks exactly like a spam operation to inbox providers, regardless of intent. Sending smaller volumes to your most-engaged contacts first, then scaling up over a couple of weeks, builds the sender reputation that lets later, larger sends actually land.
The habit that matters most
Segment your list by real engagement, and send less often to people who don't open anything. It feels counterintuitive to email fewer people, but a list that opens and clicks consistently is what keeps your domain out of spam folders for everyone else on it too.