Emails usually go to spam because of sender reputation and technical set-up rather than wording: a new domain sending too much too soon, missing SPF, DKIM or DMARC records, invalid addresses that bounce, tracking pixels and heavy HTML, no unsubscribe link or recipients who never engage. Each cause below has a fix.
Which terms do you need to know?
- Hard bounce
- A permanent delivery failure, for example because the address does not exist. The address should never be emailed again.
- Spam rate
- The share of delivered messages that recipients mark as spam. Gmail shows it in Postmaster Tools.
- List-Unsubscribe
- An email header that lets mail apps offer an unsubscribe button. The one-click version is defined in RFC 8058.
Google's sender guidelines ask bulk senders, those sending more than 5,000 messages a day to Gmail accounts, to authenticate with SPF, DKIM and DMARC, offer one-click unsubscribe and keep the spam rate below 0.1%, never reaching 0.3%. Smaller senders are judged by the same signals.
1. Is your sending domain too new?
The most common cause. A new address or domain that sends in bulk from day one has no history, and providers read the sudden volume as spam. Fix: give the address a preparation period of 14 to 21 days and raise volume gradually. Details: how to build sending reputation for a new domain.
2. Are SPF, DKIM or DMARC records missing?
These records prove that the server sending in your name is allowed to. Without them, Gmail and Outlook either file the message as spam or reject it. Fix: set up all three and check that they pass. See our guide to SPF, DKIM and DMARC.
3. Are you sending too much, too fast?
Even a sending address with a good history suffers from a blast of hundreds of emails within minutes. Fix:set a daily limit, spread sending over working hours and leave random intervals between messages. “Send all now” is the most harmful pattern.
4. Is your bounce rate too high?
A list with many invalid addresses produces hard bounces, which tells providers that the sender does not keep its list clean. Fix: verify the list before sending, add every hard-bounced address to a suppression list at once and never send to it again. Pause the campaign if the bounce rate passes a threshold such as 3%.
5. Do your emails carry tracking pixels or heavy HTML?
The invisible pixel used for open tracking and image-heavy HTML are among the signals spam filters look for. Fix: do not use open-tracking pixels and make plain text the default. Use images and links sparingly. A plain message is delivered more reliably and reads more like a person wrote it.
6. Do your content and links look like spam?
“FREE” in capitals, rows of exclamation marks, shortened links, a single large image and links to domains with a poor reputation all count against you. Fix: a clear, honest subject line, one call to action and links to your own domain.
7. Is there an unsubscribe link?
A marketing email without a way out breaks the rules in the UK and the EU and pushes recipients towards the spam button, which does the most damage to reputation. Fix: a visible unsubscribe link in every email and a one-click List-Unsubscribe header. Anyone who unsubscribes goes on the suppression list straight away. The legal side is covered in our guide to emailing trade fair exhibitors legally.
8. Are you sending cold outreach from your main domain?
If first-contact campaigns go out from your company's main domain, any damage to its reputation also affects your everyday business email. Fix: use a separate sending domain that has completed its preparation period, and keep the main domain out of the risk.
9. Do recipients ignore your emails?
Providers treat replies and other positive reactions as reputation signals. Emails sent to an unsuitable list get little response, and delivery gets worse over time. Fix: write only to companies for which your offer is relevant, give one concrete reason to reply and say who the message is for when you write to a general address such as info@.
What does the checklist look like?
| Cause | Fix |
|---|---|
| New domain | Preparation period of 14 to 21 days, rising volume |
| Missing authentication | SPF, DKIM and DMARC that pass |
| Bulk blasts | Daily limit, sending spread over working hours |
| Bounces | Verification before sending, suppression of hard bounces |
| Pixels and heavy HTML | Plain text by default, no open tracking |
| Spammy content | Honest subject line, one call to action |
| No way out | Visible unsubscribe link and one-click header |
| Main domain | A separate sending domain |
| Low engagement | Relevant companies, a clear reason to reply |
Deliverability is a discipline, not a setting
Staying out of spam depends on a set of habits rather than one switch. In Expomatik, Secure Mail enforces them in the system: separate sending domains with SPF, DKIM and DMARC, a preparation period, a fixed daily limit, no tracking pixel, and an automatic pause when the bounce rate exceeds the threshold.
Frequently asked questions
- Why do my emails go to spam in Gmail but not in Outlook?
- Each provider filters with its own signals and its own view of your reputation. A message can pass at one provider and fail at another. Check your authentication results in the message headers and the spam rate in Google Postmaster Tools.
- Can a single word in the subject line send an email to spam?
- Rarely on its own. Modern filters weigh reputation, authentication and recipient behaviour far more than single words. Wording still matters as one signal among many, so avoid capitals, repeated exclamation marks and misleading subject lines.
- How do I get my emails out of spam again?
- Fix the cause first: authentication records, list quality, volume or missing unsubscribe links. Then send lower volumes to recipients who are likely to engage and raise them gradually. Recovery takes weeks rather than days.