Why does my email land in spam?

Spam is not a judgement on your content but the result of a calculation. Four factors do most of the work.

Authentication

Without correct SPF, DKIM and DMARC your message is suspect from the start. This is the most common cause and the easiest to fix.

Your reputation

Mail providers remember how recipients respond to your sending. Many deletions without opening, or reports as spam, lower your chances for a long time.

The quality of your list

Sending to dead addresses is the strongest negative signal there is. An old list that was never cleaned damages you with every send.

The content

It matters less than people think, but a message that is one large image, shortened links, or a recently registered sending domain all worsen the score.

Where to start

Check authentication first, then clean your list. Rewriting your copy before that changes nothing.