You hit send, the email looks perfect, and then a client tells you they "never got it" before finding it buried in junk. If you have been asking why are my emails going to spam, the honest answer is that mailbox providers like Gmail, Outlook and Yahoo score every message you send against dozens of signals, and it usually only takes two or three weak ones to push you into the spam folder. There’s a good explainer over at one.com.
This guide walks through the eleven causes we see most often when we audit email setups for small businesses, and pairs each one with a concrete fix you can apply in your own DNS settings or email platform. No jargon dumps, no vague "improve your reputation" advice. Work through it in order and most senders see inbox placement recover within a couple of weeks.
Quick diagnosis: find your problem in 60 seconds
Before you change anything, match your symptom to the likely cause below.
| What you are seeing | Most likely cause | Jump to fix |
|---|---|---|
| Every email goes to spam, even one to one replies | Broken authentication or a blacklisted domain / IP | Fixes 1, 2, 3 and 8 |
| Newsletters go to spam, personal emails are fine | List quality, engagement or content triggers | Fixes 5, 6, 7 and 9 |
| It started suddenly with no changes on your side | Reputation drop, spam complaints, or a compromised mailbox | Fixes 7, 8 and 11 |
| Only Outlook or Hotmail addresses are affected | Microsoft filtering, missing DMARC or low engagement | Fixes 3, 8 and 10 |
| A brand new domain or platform is going to spam | No sending history, no warm up | Fix 4 |
How spam filters actually decide
Modern filters weigh four broad categories. Understanding them stops you wasting time on myths like "never use the word free".
- Identity: can the receiving server prove the email really came from your domain? This is SPF, DKIM and DMARC.
- Reputation: how have recipients historically reacted to mail from your domain and IP address?
- Engagement: do people open, reply, click and move your mail out of junk, or delete and complain?
- Content and structure: does the message look like the kind of thing spammers send, technically and visually?
Authentication is a pass or fail gate. Everything else is a sliding scale. That is why a perfectly worded email from an unauthenticated domain still lands in junk.
The 11 reasons your emails go to spam (and how to fix each one)
1. Your SPF record is missing, wrong, or has too many lookups
SPF (Sender Policy Framework) is a DNS record listing which servers are allowed to send email using your domain. If Mailchimp, Brevo, your CRM or your website contact form sends on your behalf and is not listed, receivers see a mismatch. Background reading: https://valimail.com.
The fix:
- Check your current record with a free tool such as MXToolbox or dmarcian by looking up your domain’s TXT records.
- Make sure you have one single SPF record, not two. Multiple SPF records cause an automatic fail.
- Include every sending service. A typical record looks like
v=spf1 include:_spf.google.com include:servers.mcsv.net ~all. - Keep DNS lookups under the limit of 10. If you are over, remove services you no longer use or use an SPF flattening service.
- End with
~all(softfail) or-all(hardfail). Never use+all.
2. DKIM is not enabled on your sending platform
DKIM adds a cryptographic signature that proves the message was not altered in transit and genuinely came from your domain. Many small businesses set up SPF and stop there. Gmail and Yahoo both expect DKIM from bulk senders, and Microsoft has tightened its requirements for high volume senders too.
The fix: in your email platform, find the domain authentication or sending domain section, generate the DKIM keys, and publish the CNAME or TXT records your provider gives you in your DNS.
- Google Workspace: Admin console, Apps, Google Workspace, Gmail, Authenticate email. Use a 2048 bit key.
- Microsoft 365: Defender portal, Policies, Email authentication settings, DKIM, then enable for your custom domain.
- Mailchimp, Brevo, Klaviyo, ActiveCampaign, HubSpot: all have a "verify domain" or "authenticate domain" wizard that outputs the records.
Send a test to a Gmail account, open it, click the three dots and choose "Show original". You want to see PASS next to SPF, DKIM and DMARC.
3. You have no DMARC record
DMARC tells receivers what to do when SPF and DKIM fail, and it is now effectively mandatory. Since the bulk sender rules introduced by Google and Yahoo, and Microsoft’s follow up for senders of 5,000 or more messages a day, a domain with no DMARC policy is treated with suspicion.
The fix: add a TXT record at _dmarc.yourdomain.co.uk.
| Stage | Record value | What it does |
|---|---|---|
| Start here | v=DMARC1; p=none; rua=mailto:[email protected] |
Monitors only, sends you reports, changes nothing |
| After 2 to 4 weeks | v=DMARC1; p=quarantine; pct=25; rua=... |
Sends a quarter of failing mail to junk |
| Once clean | v=DMARC1; p=reject; rua=... |
Blocks anyone spoofing your domain |
Do not jump straight to p=reject. Monitor first, confirm every legitimate sender passes, then tighten. Also check alignment: the visible From domain must match the domain that passed SPF or DKIM.
4. You are sending from a brand new domain or a cold IP with no warm up
A domain registered last month that suddenly sends 5,000 emails looks exactly like a throwaway spam domain. Reputation is earned through consistent, low volume sending.
The fix: warm up gradually over three to four weeks.
- Days 1 to 3: send 20 to 50 emails a day to your most engaged contacts, ideally people who will reply.
- Week 2: double daily volume every two days, staying under 1,000.
- Week 3 onwards: keep increasing while watching bounce and complaint rates.
- Never send your entire list on day one from a new domain or platform.
If you use a subdomain for marketing, such as news.yourdomain.co.uk, warm that up separately. It protects your main domain reputation for invoices and client replies.
5. Your list was bought, scraped or imported without permission
This is the fastest way to destroy a good domain. Purchased lists contain spam traps, recycled addresses that mailbox providers use specifically to catch senders who did not collect consent. Hitting one can get your domain blacklisted immediately.
The fix:
- Delete any purchased or scraped data. There is no safe way to mail it.
- Use confirmed opt in for new subscribers so every address is verified and provable.
- For contacts you have a genuine business relationship with under UK GDPR and PECR, send a short re-permission email rather than a full campaign.
- If you must do cold outreach, do it one to one from a separate domain, in low volumes, with a clear opt out.
6. Your subject line and content look like spam
Content alone rarely causes filtering, but it tips the balance when other signals are weak. Filters look at patterns, not a banned word list.
Avoid:
- ALL CAPS subject lines and rows of exclamation marks
- Urgency stacking such as "ACT NOW!!! LIMITED TIME OFFER, 90% OFF, RISK FREE"
- Emails that are one large image with almost no text
- Link shorteners like bit.ly, which spammers use to hide destinations
- Attachments in bulk mail, especially .zip, .exe or unexpected PDFs
- Mismatched links where the text says one domain and the href points to another
Do instead: write a plain, specific subject line, keep a healthy text to image ratio of roughly 60:40 or better, use full branded links on your own domain, include a plain text version alongside your HTML, and make sure the HTML is clean and not pasted out of Word.
Run a draft through a free tool like mail-tester.com before you send. It scores your message out of 10 and lists the exact triggers.
7. Low engagement is telling Gmail nobody wants your email
Gmail in particular is heavily engagement driven. If your open rates are falling and nobody clicks or replies, your mail slides from Primary to Promotions to Spam.
The fix:
- Segment by activity. Send your regular campaigns to people who opened or clicked in the last 90 days.
- Run a single win back campaign to the inactive segment, then suppress everyone who still does not engage.
- Ask for a reply in your welcome email. Replies are one of the strongest positive signals there is.
- Reduce frequency if you are sending daily to a list that only wants monthly.
- Ask new subscribers to add your address to their contacts, and if you use Gmail, to drag your email into Primary.
8. Your domain or IP is on a blacklist
A compromised mailbox, a hacked website form or an old campaign can land you on a blocklist such as Spamhaus, SURBL or Barracuda. Everything then goes to junk overnight.
The fix:
- Check your domain and sending IP at MXToolbox Blacklist Check or Spamhaus.
- If listed, find the cause first. Change all mailbox passwords, enable two factor authentication, secure or remove any open contact and comment forms, and scan your site for malware.
- Submit a delisting request only once the cause is fixed. Most listings expire automatically if the bad behaviour stops.
- Register for Google Postmaster Tools and Microsoft SNDS so you can watch your reputation instead of guessing.
9. Hard bounces and stale addresses are dragging you down
A bounce rate above roughly 2 percent tells receivers you do not maintain your list. Complaints above 0.3 percent are a hard fail against Google and Yahoo’s published thresholds.
The fix:
- Remove hard bounces immediately. Most platforms do this automatically, but check the setting is on.
- Run your list through a verification service before any large send, especially if it has been sitting unused for six months or more.
- Suppress role addresses such as info@, sales@ and admin@ in marketing campaigns.
- Add a honeypot field or CAPTCHA to signup forms to stop bot submissions poisoning your list.
10. There is no easy unsubscribe, so people hit the spam button instead
Every spam complaint is a direct hit to your reputation. Hiding the unsubscribe link does not keep subscribers, it just converts them into complainers.
The fix:
- Put a visible unsubscribe link in the footer of every marketing email.
- Enable one click list unsubscribe headers in your platform. This is a requirement for bulk senders and adds the native unsubscribe button next to your name in Gmail.
- Process opt outs within two days, not two weeks.
- Offer a preference centre so people can reduce frequency instead of leaving entirely.
11. Technical and infrastructure mistakes
These are the ones people miss because they sit outside the email platform.
- Sending "from" a Gmail or Yahoo address through a bulk platform. Because of DMARC policies at those providers, this fails alignment. Always send from your own domain.
- No PTR / reverse DNS record if you send from your own server. Receivers expect the IP to resolve back to a hostname.
- Missing MX record or no working reply mailbox. If mail to your From address bounces, you look fake.
- Shared IP with bad neighbours on cheap hosting or a low cost sender. Move to a reputable ESP.
- Your website contact form sending as the visitor’s address. Set the From to your own domain and put the visitor address in Reply-To.
- Expired or misconfigured TLS. Encrypted connections are now expected.
Your 7 day deliverability recovery plan
| Day | Action |
|---|---|
| 1 | Audit SPF, DKIM and DMARC. Send a test to Gmail and check "Show original" for three PASS results. |
| 2 | Run a blacklist check on your domain and IP. Fix any compromise before requesting delisting. |
| 3 | Set up Google Postmaster Tools and Microsoft SNDS. Add DMARC reporting to a monitored inbox. |
| 4 | Clean the list. Remove bounces, unengaged contacts over 12 months, and any imported data with no consent record. |
| 5 | Rewrite your template. Better text to image ratio, branded links, plain text version, visible unsubscribe. |
| 6 | Score a draft on mail-tester.com and fix anything below 9 out of 10. |
| 7 | Send to your most engaged 20 percent only. Rebuild from there over the following fortnight. |
Benchmarks to aim for
| Metric | Healthy | Danger zone |
|---|---|---|
| Spam complaint rate | Under 0.1% | Over 0.3% |
| Hard bounce rate | Under 1% | Over 2% |
| Unsubscribe rate | Under 0.5% | Over 1% |
| Open rate (small business average) | 20% or higher | Under 10% |
Frequently asked questions
How do I stop my emails from going to spam?
Authenticate your domain with SPF, DKIM and DMARC, send only to people who opted in, keep your list clean of bounces and inactive contacts, include a working one click unsubscribe, and avoid image only emails with hype heavy subject lines. Authentication is the first step because it is pass or fail.
Why are my emails going to spam all of a sudden?
Sudden changes usually mean one of four things: a DNS record was edited or expired, your mailbox or website was compromised and used to send spam, you were added to a blocklist, or you sent to a large batch of old, unengaged addresses that generated complaints. Check authentication and blacklists first.
Why do my emails go to spam in Gmail but not Outlook?
Gmail leans heavily on engagement signals and its own reputation history for your domain. Outlook weights authentication, IP reputation and complaint volume differently. If only Gmail is affected, focus on engagement, list segmentation and asking recipients to reply or move you to Primary.
Does DMARC really stop emails going to spam?
DMARC on its own does not guarantee inbox placement, but not having it is now a clear negative signal, especially for anyone sending in volume. It also stops criminals spoofing your domain, which protects the reputation you are trying to build.
How do I unspam my email address?
Ask a few contacts to open the spam folder, select your message and click "Not spam" or "Report not junk", then add your address to their contacts. Combine that with fixing the underlying cause, otherwise you will end back in junk within a couple of sends.
How long does it take to recover sender reputation?
Expect two to six weeks of consistent, well received sending. Reputation recovers slowly and drops quickly, so keep volumes modest and target engaged contacts while you rebuild.
Should I use a subdomain for marketing emails?
Yes, for most businesses it is worth it. Sending campaigns from something like news.yourdomain.co.uk keeps marketing reputation separate from the transactional and personal mail sent from your main domain, so a bad campaign will not stop invoices reaching clients.
Need a hand?
Email deliverability sits right where DNS, hosting and marketing overlap, which is exactly why it gets left half finished. If you would rather someone audited your records, checked your blacklist status and set your DMARC policy up properly, get in touch with the Komodo Media team and we will take a look at your setup.