Few things are more frustrating than a customer saying “your quote went to my spam folder”. The fix is rarely one magic setting. Spam filters weigh many signals, but a handful of them do most of the work. Here are the causes we see most often, in order of impact.
1. Missing or broken SPF, DKIM or DMARC
This is the number one cause for small businesses. Without these records, receiving servers can’t confirm that your mail is really from you, so they treat it with suspicion. Since 2024, Gmail and Yahoo require authentication for anyone sending in bulk, and they trust authenticated mail more in general.
Fix: add all three records and check them in your dashboard. Our guide to MX, SPF, DKIM and DMARC explains each one.
2. Two SPF records, or SPF that doesn’t include your sender
If your website, billing software or newsletter tool sends email as your domain but isn’t listed in SPF, that mail fails the check. And if you created a second SPF record to “add” a service, both are ignored.
Fix: keep exactly one SPF record listing every service that sends as your domain.
3. Sending from a free address through another service
Sending as yourname@gmail.com from a website contact form or a marketing tool fails Gmail’s own DMARC policy. Fix: send from an address on your own domain.
4. People mark your mail as spam
Recipient behaviour is a huge signal. Google asks bulk senders to keep their spam-complaint rate below 0.1% and never let it reach 0.3%. Complaints usually come from sending to people who never asked for your mail, or making it hard to unsubscribe.
Fix: only email people who agreed to hear from you, and include a clear one-click unsubscribe link. WhySharedMail campaigns add this automatically.
5. Old or bought contact lists
Old lists contain addresses that no longer exist (bounces) and “spam traps” — addresses that only exist to catch senders with poor list hygiene. Bought lists are worse. Fix: never buy lists; remove addresses that bounce.
6. Sudden bursts of email
Sending 2,000 emails at once from a domain that normally sends 20 a day looks like a compromised account. Fix: send in batches and grow volume gradually — campaign tools with hourly limits do this for you.
7. Content that looks like spam
- Subject lines in ALL CAPS or with lots of !!!
- An email that is one big image with almost no text
- Link shorteners or many links to different domains
- Attachments like .zip or .exe
Fix: write like a person, use a balance of text and images, and link to your own website.
8. No plain-text version
Good emails include both HTML and a plain-text version. Most email tools, including our campaign editor, create the plain-text part automatically.
9. Mismatched “From” name and address
A message from “HDFC Bank” sent by offers@randomdomain.xyz looks like phishing. Use a sender name that matches your business and domain. You can set a clear sender name for each mailbox in your dashboard.
10. Your mail server or IP has a poor reputation
If you send through a cheap shared server that others abuse, your mail suffers too. A reputable email host monitors this and limits abuse.
Quick checklist
- MX, SPF, DKIM and DMARC all show a green tick
- Only one SPF record
- Sending from your own domain, with a real sender name
- Only opted-in recipients, with unsubscribe links
- Gradual sending, text-and-image balance, no shortened links
Work through this list and most businesses see their mail back in the inbox within days. Need a reliable starting point? See our business email plans.
Frequently asked questions
Why do my emails go to spam in Gmail but not in Outlook?
Each provider uses its own filters and reputation data. Gmail weighs authentication (SPF, DKIM, DMARC) and how recipients react to your mail very heavily, so fix those first.
Does using words like “free” send my email to spam?
A single word rarely decides it. Modern filters look at authentication, sender reputation and recipient behaviour much more than individual words, but shouting, too many links and image-only emails do hurt.
How long does it take to fix spam problems?
Missing DNS records start helping within hours. Rebuilding a damaged sender reputation can take a few weeks of sending wanted mail to engaged recipients.