Email campaigns can land in spam for many reasons: poor list quality, spammy content, low engagement, or unverified domains. This article shows you how to prevent spam placement and recover if it's already happening.
Before You Begin
Before troubleshooting spam issues, verify the following:
Check domain authentication: Ensure SPF, DKIM, and DMARC are set up. Set up domain authentication.
Confirm spam placement: Send test campaigns to Gmail, Yahoo, and Outlook. Check inbox, promotions, and spam folders.
Monitor metrics: Set up Google Postmaster Tools to track spam rate and domain reputation.
💡 Tip: Low open rates don't always mean spam. Verify actual folder placement before troubleshooting.
Spam Prevention Best Practices
To make sure none of your emails end up in spam, you should use preventive tactics for email marketing.
1. Use Only Opted-In Contacts
Your sender reputation and email deliverability depend entirely on the quality of your contact list. Never rent, buy, share, scrape, or co-register email lists. Sending emails to recipients who have not explicitly consented to receive your messages leads to spam complaints, damages your sender reputation, and reduces inbox placement.
Your subscribers should actively agree to receive your messages and look forward to them. To build a compliant, high-quality list, collect contacts using Omnisend Signup Forms.
All major mailbox providers (Gmail, Outlook, Yahoo, AOL, etc.) monitor spam complaint rates. To maintain healthy deliverability:
Recommended spam complaint rate: 0.1% or lower (1 complaint per 1,000 emails sent).
Gmail’s maximum threshold: 0.3% (3 complaints per 1,000 emails).
Exceeding these limits can cause your future campaigns to land in the spam folder.
💡 Unsubscribes are always better than spam complaints. Make your unsubscribe link clearly visible and easy to use.
2. Clean Your Email List Regularly
Mailbox providers such as Gmail, Yahoo, and Outlook monitor recipient engagement to detect and filter spam. If subscribers consistently ignore your emails (no opens or clicks), future messages are more likely to land in spam, first for those users, and eventually affect your overall deliverability.
💡 A smaller, engaged audience performs better than a large, inactive one. List quality is more important than list size.
Best practices:
Regularly remove inactive contacts who haven't engaged with your emails.
Segment inactive contacts before removal to attempt re-engagement if needed.
Remove bounced email addresses and role-based addresses (e.g., info@, support@, sales@).
Run Email List Cleaning on a regular basis (recommended: quarterly).
⚠️ Keep your bounce rate below 4%. High bounce rates violate our Anti-Spam Policy and may result in account warnings or restrictions. Although our system automatically removes bounced emails, you must also delete contacts who did not voluntarily subscribe, are outdated, inactive, or lack an opt-in record.
How to Clean Your List in Omnisend
Step 1. Go to Reports → Deliverability → Scroll to Email list hygiene → Click Go to email list cleaning.
Step 2. Choose whether to:
Clean your entire list by clicking Clean my full list, or;
Select specific segments from the dropdown menu.
💡You can select multiple segments and clean them at once.
Step 3. Confirm the pricing and click Clean My List. The service costs $0.20 per 100 contacts, calculated automatically based on your selected audience.
⚠️ Once the cleaning process starts, it cannot be canceled.
You can pay using Google Pay, Link (bank payment), or a credit card. You may also save your payment details for future use.
Step 4. After analysis, choose one of the following options:
Automatically unsubscribe poor-quality contacts: Omnisend will automatically unsubscribe all identified poor-quality contacts. You will still have the option to review and unsubscribe from additional groups, such as disposable or unknown email addresses.
Manually unsubscribe poor-quality contacts: You will receive a detailed breakdown of the contact analysis and can manually review and unsubscribe poor-quality contacts or other groups (e.g., disposable, unknown), as described in Step 5.
Step 5. If you choose manual review, you’ll see a detailed breakdown of contact categories. Click Show Contacts under each category to view them.
From this screen, you can:
Unsubscribe contacts in bulk;
Tag contacts;
Download contact lists.
That's it! Select the groups of contacts you want to clean → Unsubscribe contacts. Your list is cleaned.
💡 You can access past cleaning results anytime from the main List Cleaning tab; all cleaning history is saved for reference.
3. Migrating to Omnisend? Warm Up First
If you’ve recently migrated to Omnisend and using your custom sender domain, do not send to your entire contact list on day one. Mailbox providers evaluate your sending infrastructure even if your contacts were highly engaged on your previous platform.
Sending to your full list immediately can trigger spam filters and negatively impact your sender reputation from the start. Instead, gradually increase your sending volume to build trust with inbox providers.
Sender Domain Best Practices
Use a Custom Domain for Your Sender Email Address
Always send emails from your own domain (e.g., [email protected]), not from free providers such as Gmail, Yahoo, Outlook, or AOL. Mailbox providers often reject or filter emails sent from free domains. In Omnisend, using addresses like [email protected] is not allowed.
Ensure your custom sender domain is assigned to both campaigns and automations. If campaigns use your custom domain but automations use a shared domain, mailbox providers may detect inconsistent sending behavior, which can damage your reputation.
Manage Your Domain Reputation
If you previously sent bulk emails directly from your domain before using Omnisend, your domain reputation may be compromised.
Check whether your domain is blacklisted using a blacklist monitoring tool such as MXToolbox. Enter your domain name (e.g., yourstore.com) and run a blacklist check.
If your domain is listed, request removal before launching campaigns. Sending from a blacklisted domain will cause your emails to land in spam.
Email Content Best Practices
Avoid Spammy Content
Spam filters analyze how your content is written. Avoid the following:
Excessive use of exclamation points (!!!!!!).
Writing subject lines or body text in ALL CAPS.
Misleading or overly aggressive phrases such as “Click here!” or “Once in a lifetime opportunity!”.
Hash-busting techniques (e.g., “F.ree. p.r!z.e”).
Overusing sales-trigger words like “free,” “prize,” or “bonus”.
You can still use promotional language, but keep it natural and moderate. Overuse increases the risk of spam filtering.
Maintain a Healthy Text-to-Image Ratio
Avoid sending image-only emails. Spam filters evaluate the balance between text and images.
Include at least 2–4 sentences of text per image to provide context for both mailbox providers and recipients.
Be Aware of Gmail Clipping
Gmail clips emails larger than 100KB. When this happens, recipients must click “View entire message” to see the full content.
The 100KB limit includes all email elements:
Text;
Images;
Links;
Tracking codes;
Responsive design elements.
If the unsubscribe link is placed below the clipped section, recipients may click “Report Spam” instead, which negatively impacts your sender reputation.
💡 When creating separate mobile and desktop layouts, ensure the total email size remains under 100KB. Keep your content concise and optimized.
Troubleshooting Emails Already in Spam
Confirm Spam Placement First
Low open rates don't always mean spam. Verify by:
Sending test campaigns to Gmail, Yahoo, Outlook;
Checking inbox, promotions, and spam folders;
Reviewing Google Postmaster Tools for spam rate spikes.
Recovery Steps
If emails are landing in spam, recovery takes 2–4 weeks or longer. Follow these steps:
Stop sending to your full list immediately.
Send only to highly engaged contacts (opened in last 30 days).
Gradually increase volume by 25–35% per campaign.
Monitor Google Postmaster Tools daily for spam rate and reputation improvements.
Avoid spam triggers (caps, misleading subject lines, excessive links).
Note: Even with perfect changes, emails may still land in spam initially. Mailbox providers need consistent positive engagement (opens, clicks, low spam complaints) to rebuild trust.
When to Contact Support
If the above steps don't work after 2–4 weeks, contact our Support Team at [email protected] or use in-app chat. Our Deliverability team may recommend verifying SPF/DKIM records, moving to a dedicated IP (additional charges may apply), or advanced troubleshooting.
FAQ
Why do my emails go to spam even though SPF, DKIM, and DMARC are verified?
Domain authentication proves your identity, but doesn't guarantee inbox placement. Mailbox providers also evaluate:
Recipient engagement (opens, clicks, replies);
Spam complaint rate (keep below 0.1%);
List quality (no inactive or invalid contacts);
Sending consistency (gradual volume increases).
Even with a perfect DNS setup, poor engagement or high complaints will send emails to spam.
Why does the same email land in the inbox for some recipients but in spam for others?
Mailbox providers personalize delivery for each recipient based on their past engagement with your emails. If a recipient frequently opens your emails, they land in the inbox. If they ignore or mark as spam, future emails go to spam or promotions.
How long does it take to recover from a spam reputation drop?
Recovery typically takes 2–4 weeks or longer. Send only to engaged users (opened last 30 days), increase volume gradually (25–35% per campaign), and monitor Google Postmaster Tools daily. Mailbox providers need consistent positive engagement to rebuild trust.
If you have more questions, contact us at [email protected] or via in-app chat.