Why are my emails going to spam?

How spam filters decide

Mailbox providers do not use a single test. They combine many signals into a judgement about each message: whether the sender is who they claim to be, how recipients have treated this sender's mail in the past, and what the message itself looks like. Authentication is the part you can check mechanically. Reputation and content take longer to change.

The causes below are roughly ordered from fastest to fix to slowest.

Technical causes you can check right now

• No or broken [SPF](/spf-checker). The receiver cannot tell whether the sending server is allowed to use your domain. Two records, more than 10 DNS lookups, or a missing sender all cause failures.
• No [DKIM](/dkim-checker) signature. Without a valid signature, mail cannot be tied cryptographically to your domain. Gmail and Yahoo require it from bulk senders.
• No [DMARC](/dmarc-checker) record. Without one, receivers have no policy for failures, and bulk senders to Gmail and Yahoo are required to publish one.
• Alignment failures. SPF and DKIM pass, but for a provider's domain rather than yours, so DMARC fails.
• Missing reverse DNS. Sending IPs without a PTR record that resolves back to the IP look like hijacked machines. This is one of the basic requirements Gmail lists.
• A [blacklisted](/email-blacklist-check) sending IP. Often caused by a compromised account or a shared IP with a bad neighbour.
• No TLS when connecting to the receiver.

Scanning your domain here covers SPF, DKIM, DMARC, reverse DNS, blacklists and several newer standards, and gives each problem a fix in plain English.

Reputation and sending behaviour

• New domain or IP with no history. Providers are cautious about senders they have not seen before. Start with small volumes to engaged recipients and increase gradually, which is known as warming up.
• Sudden volume spikes. A domain that sends 50 emails a day and then 50,000 looks suspicious.
• Spam complaints. When recipients click "report spam", providers learn from it. Google asks senders to keep the spam rate shown in Postmaster Tools under 0.30%, and recommends staying lower still.
• High bounce rates. Mailing addresses that do not exist signals a poor-quality list.
• Purchased or scraped lists. They contain spam traps and uninterested people, and they damage reputation quickly.
• Low engagement. Providers notice when people never open or reply to your mail, or when they delete it unread.

Content and formatting

• Misleading subject lines or a From name that does not match the sending domain.
• Messages that are one large image with almost no text.
• Links to URL shorteners or to domains with a poor reputation.
• Broken HTML or a missing plain-text alternative.
• No clear way to unsubscribe in marketing email. Gmail and Yahoo require one-click unsubscribe for bulk senders.
• Sending as a free-mail address such as @yahoo.com from your own server. Yahoo publishes a DMARC policy of reject, so mail that claims to be from it but is not sent by it is refused.

Old advice about "spammy words" is less important than authentication, list quality and engagement. A technically perfect message to people who do not want it still ends up in spam.

A practical order of fixes

1. Scan your domain and fix any failing SPF, DKIM or DMARC results first. These are DNS edits that take effect within hours.
2. Check that sending IPs have reverse DNS and are not on a blocklist.
3. Send a test message to a Gmail account, open "Show original" and confirm SPF, DKIM and DMARC all say PASS.
4. Register your domain with Google Postmaster Tools and watch spam rate and domain reputation.
5. Clean your list: remove addresses that bounce or never engage, and send only to people who asked to hear from you.
6. Add a visible unsubscribe link and the one-click unsubscribe headers for marketing mail.

A domain scan cannot see your content, your sending volumes or how recipients react to your mail. If the technical checks are clean and you still land in spam, reputation and list quality are the next place to look.