Why Does My Email Go to Spam?

Acutis · plain-English network help · updated June 2026

The short answer

If your email keeps landing in the spam folder, it is almost never about the words you wrote. In the overwhelming majority of cases the cause is one of three things: your domain's authentication records (SPF, DKIM and DMARC) are missing or broken, the server you send from has a bad reputation or is on a blacklist, or the content and sending pattern of your mail looks like spam to the filters. The good news is that all three are diagnosable and fixable. This guide walks through each, then gives you a checklist to run down.

Cause 1: Missing or misaligned authentication

This is the single biggest reason legitimate mail gets filtered. Modern providers like Gmail and Outlook quietly distrust any domain that can't prove its mail is genuine. Three records do that proving, and a gap in any of them hurts you:

• SPF missing or broken. SPF is the public list of servers allowed to send for your domain. No record — or a broken one that exceeds the ten-lookup limit, or two records on one domain — and receivers lose trust fast.
• DKIM not signing. DKIM is the cryptographic seal that proves a message is genuine and unaltered. If your mail isn't being signed, or the key in DNS is wrong, that proof is missing.
• DMARC absent or misaligned. DMARC ties SPF and DKIM together and demands they match your visible "From" address (alignment). Without it, even passing checks can fail to add up, and spoofers have an easy time.

If you only fix one thing today, fix these. A domain with clean, aligned SPF, DKIM and DMARC clears the highest bar filters apply.

Cause 2: A blacklisted or low-reputation sending IP

Every sending server has a reputation, and email providers track it closely. If the IP address you send from has been used for spam — even before you used it — your mail inherits the suspicion. Common reasons a sending IP goes bad:

• Blacklist listings. Public blocklists (such as Spamhaus) flag IPs seen sending spam. If your shared host's IP is listed, your mail suffers alongside everyone else on it.
• A cold or shared IP. A brand-new IP with no sending history, or a cheap shared one used by many senders, carries little or negative trust.
• Sudden volume spikes. Going from a handful of emails a day to thousands overnight looks exactly like a compromised account, and filters react accordingly.

You can check your sending IP against the major blacklists, and if you are listed, most maintain a delisting process once the underlying issue is resolved.

Cause 3: Content and sending behavior

Once authentication and reputation are healthy, content is the last lever. Filters look at the shape of the message, not just the words, so a few habits make a real difference:

• Spam-trigger formatting. ALL CAPS subject lines, "FREE!!!", excessive exclamation marks, and one giant image with almost no text all raise flags.
• Bad links and mismatched URLs. Link shorteners, links to flagged domains, or visible text that doesn't match where the link actually goes.
• No easy unsubscribe. For bulk mail, a missing or hidden unsubscribe option both breaks the rules of major providers and drives the spam complaints that wreck your reputation.
• Recipients marking you as spam. The strongest negative signal of all. Send only to people who expect your mail, and the complaint rate stays low.

The fix-it checklist

Work down this list in order. The early items fix the most cases:

1. Publish a valid SPF record that lists every service you send from, ending in ~all (or -all once you're sure).
2. Turn on DKIM signing in your mail provider and publish the _domainkey record it gives you.
3. Add a DMARC record at _dmarc.yourdomain.com, starting at p=none with a rua reporting address, then tighten over time.
4. Check your sending IP against the major blacklists and request delisting if needed.
5. Clean up your content — plain, honest subject lines, a real text-to-image balance, and a working unsubscribe link on bulk mail.
6. Send only to engaged recipients and warm up new volume gradually rather than all at once.
7. Confirm your network and DNS are healthy, so the records you publish actually resolve and your mail server can be reached.

Run that list top to bottom and the large majority of spam-foldering clears up. The first three items alone solve most of it.