Why Are My Business Emails Going to Spam?

When your business emails consistently land in spam, it damages your credibility, loses you customers, and creates a frustrating cycle that's hard to break out of. The good news is that most spam filter issues have identifiable causes and straightforward fixes.

Here are the most common reasons your emails are being filtered, in rough order of likelihood.

1. Missing or Misconfigured SPF, DKIM, or DMARC Records

This is the single most common cause of legitimate emails going to spam. If your domain doesn't have proper email authentication records, receiving servers have no way to verify that your emails are genuine.

• SPF tells receivers which mail servers are authorised to send from your domain
• DKIM adds a cryptographic signature proving the email hasn't been tampered with
• DMARC tells receivers what to do if SPF or DKIM checks fail

Without these records, your emails look no different from spoofed or phishing emails. Gmail, Outlook, and other providers will default to treating them as suspicious.

For a full explanation of how these records work and how to set them up, see our guide on SPF, DKIM, and DMARC.

2. Poor Sender Reputation

Every domain and IP address that sends email builds up a sender reputation score. This score is based on factors like:

• How many recipients mark your emails as spam
• How many emails bounce (invalid addresses)
• Whether people actually open and engage with your emails
• How quickly you remove subscribers who complain
• Whether you send to purchased or scraped email lists

If your sender reputation drops below a certain threshold, spam filters will start filtering your emails aggressively — even to people who want to receive them.

Building a good reputation takes time. The key is: only send to people who have explicitly opted in, remove bounced addresses immediately, honour unsubscribe requests promptly, and maintain consistent sending patterns (don't suddenly send thousands of emails if you normally send ten).

3. Shared IP Address with Bad Reputation

If you use a shared hosting provider or an email marketing service, you're probably sending from a shared IP address. This means other companies using the same IP affect your reputation.

If another company on your shared IP sends spam, gets blacklisted, or generates high complaint rates, your emails can be caught in the fallout. This is one of the most frustrating causes because it's entirely outside your control.

Solutions include: switching to a dedicated IP address (most email marketing providers offer this for an additional cost), requesting a different shared IP from your provider, or moving to a provider with better IP reputation management.

4. Email Content Triggering Spam Filters

Spam filters analyse the content of your emails. Certain patterns will increase your spam score:

• Spam trigger words: "FREE", "GUARANTEED", "NO OBLIGATION", "ACT NOW", "LIMITED TIME" — especially in subject lines
• Excessive capitalisation: WRITING IN ALL CAPS or MiXiNg CaSe
• Too many links: emails with a high link-to-text ratio look suspicious
• Large attachments: executables, zip files, or unusually large files
• Mismatched links: the visible link text says one domain but the actual URL points somewhere different
• Poor HTML formatting: broken HTML, missing plain-text version, or emails that are a single large image

The fix isn't to avoid all marketing language, but to be measured. Write natural subject lines, use links sparingly, include a plain-text alternative, and keep your HTML clean.

5. Missing or Misconfigured Reverse DNS (rDNS)

Reverse DNS maps an IP address back to a hostname. When your mail server sends an email, the receiving server performs a reverse DNS lookup on your IP address. If the lookup doesn't match the hostname in your email's HELO/EHLO greeting, the email may be rejected or filtered.

This is especially common with self-hosted mail servers or VPS providers where rDNS isn't configured by default. Most major email providers (Google Workspace, Microsoft 365) handle this automatically.

If you manage your own mail server, configure rDNS through your hosting provider's control panel or by contacting their support. The PTR record should point your server's IP address to its hostname, and that hostname should resolve back to the same IP.

6. No Proper Unsubscribe Mechanism

If you send marketing emails without a working unsubscribe link, frustrated recipients will mark you as spam instead of unsubscribing. Each spam complaint damages your sender reputation, creating a downward spiral.

Under PECR (and GDPR), you're legally required to include an unsubscribe mechanism in every marketing email. Make it prominent, easy to use, and process unsubscribe requests immediately — not in "48 hours" or "within 7 days".

How to Diagnose Spam Issues

Before you start fixing things, work out what's actually causing the problem:

1. Check your authentication records — use a free tool like MXToolbox or run a PulseShield scan to see if SPF, DKIM, and DMARC are configured correctly
2. Review bounce messages — when an email is rejected, the bounce message often tells you exactly why (missing SPF, listed on a blacklist, etc.)
3. Test with mail-tester.com — send an email to the address on mail-tester.com and it scores your email on authentication, content, and reputation
4. Check blacklists — look up your sending IP address on major DNS blacklists (Spamhaus, Barracuda, SURBL)
5. Review your DMARC reports — if you have DMARC configured with reporting, the aggregate reports show you exactly which emails are passing and failing authentication

Step-by-Step Fixes

1. Set up SPF, DKIM, and DMARC — this is the highest-impact fix. See our SPF/DKIM/DMARC guide for detailed instructions.
2. Configure reverse DNS if you manage your own mail server
3. Check and resolve any blacklists — most blacklists have a removal process
4. Clean your email list — remove bounces, inactive subscribers, and anyone who hasn't engaged in 6+ months
5. Improve your content — avoid spam triggers, include plain-text versions, keep HTML clean
6. Consider a dedicated IP if you're affected by other senders on a shared IP
7. Warm up new IPs slowly — if you switch to a new IP, gradually increase volume over 2-4 weeks

If your domain is being spoofed (someone else is sending emails that look like they're from you), this will also damage your reputation. See our guide on how to prevent email spoofing to lock down your domain.