Why are my marketing emails going to spam?

Deliverability rests on three things: proving you are who you claim to be, having a good sending reputation, and sending content people want. Failing any one is enough.

Authentication is the foundation and the most common technical gap. Three DNS records work together. SPF lists which servers may send for your domain. DKIM adds a cryptographic signature proving the message was not altered. DMARC ties them together and tells receiving servers what to do when checks fail. Major providers now effectively require all three for bulk sending, and messages without them are routinely rejected or filtered regardless of content.

Reputation is built over time and attaches to both your domain and your sending address. A new domain sending a large volume immediately looks exactly like a spammer, which is why warming up gradually matters. Reputation is damaged most by spam complaints, by sending to addresses that no longer exist, and by hitting spam traps, which are addresses maintained specifically to catch senders using purchased or scraped lists.

List quality is therefore not a nicety. Buying lists is the single fastest way to destroy deliverability, and permanently. Removing addresses that bounce, and suppressing people who never open, protects the reputation that gets your mail to everyone else.

Content factors are real but secondary. Excessive capitals and exclamation marks, a single large image with almost no text, link shorteners and mismatched sender names all contribute.

Make unsubscribing easy and obvious. Counterintuitively, a prominent unsubscribe link improves deliverability, because the alternative for an annoyed recipient is marking the message as spam, which is far more damaging.