If your emails are landing in the spam folder, the first step to resolve the issue is identifying why they're being flagged as spam
Spam filters analyze various factors to understand if your email is safe, suspicious, or spam. Key triggers include:
Poor sender reputation
Spammy language in the subject or body
Misconfigured domain settings (e.g., missing SPF/DKIM/DMARC records)
High bounce rate
Lack of recipient engagement
Unusual sending behaviour
Each email provider has its own unique spam filtering system.
This means an email that reaches the inbox in one service might be flagged as spam by another email provider
Poor sender reputation
Your sender reputation is like a trust score given to your domain or email address by mailbox providers. It’s based on how consistently and responsibly you’ve sent emails in the past.
If your reputation is low, your emails might land in spam or get blocked altogether—even if your content is great.
To protect your sending reputation:
Warm up your domain properly
Monitor your performance metrics regularly
Avoid spammy behavior
Learn more about how to warm up a new domain before starting campaigns:
Spammy language in the subject or body
Spam filters are designed to detect phrases and formatting commonly used in unwanted or malicious emails. If your message includes these elements, there is a high chance it will be flagged and moved to the recipient’s spam folder or blocked entirely.
Spammy content typically includes:
Overly promotional phrases like “Buy now,” “Act fast,” “100% free,” “Guaranteed results”
Excessive use of ALL CAPS, exclamation marks!!!, or symbols like $$$
Misleading subject lines that don’t match the email content
Use of urgent or aggressive wording that pressures the recipient
High amount of links, including URL shorteners (like bit.ly), images, logos
Domain setup
Setting up proper domain authentication is essential before starting any email campaigns. Incorrect or incomplete settings can cause your emails to be marked as spam.
Make sure your domain is authenticated according to your email provider’s requirements before starting the sending process.
Note: Since Reply is not a mail server, you don’t need to add Reply.io to your domain authentication setup
Learn more about domain setup here:
Bounce rate
Mailbox providers track your bounce rate closely. A high bounce rate indicates poor sending practices, such as:
Sending to outdated or incorrect email addresses
Using purchased or scraped contact lists
Not verifying emails before sending
When mailbox providers detect this behavior, they may lower your sending reputation, block your emails, filter them as spam, or even limit your sending volumes
To prevent a high bounce rate, take the following steps:
Check and update your prospect list regularly by removing invalid email addresses. Consider using additional validation to check the quality of your prospects before starting campaigns
Avoid purchased lists. These often contain old, inactive, or invalid addresses, and may even include spam traps
Monitor bounce reports. Analyze why emails are bouncing and take action to fix the issues quickly.
Recipient engagement
If users regularly ignore or delete your emails without opening them, that decreases your sender reputation.
Here are some strategies to keep engagement high:
Segment your list by sending relevant content to specific audiences.
Remove unengaged users who haven’t opened emails in the last 3–6 months.
Use as much personalization as possible
Sending behaviour
Maintaining a consistent sending pattern is important to ensure stable deliverability.
Avoid sudden spikes in volume, as they can trigger spam filters and harm your sender reputation.
If you plan to scale up your outreach:
Increase your daily volume slowly by using ramp-up mode to automate this growth safely
Add more warm traffic
Send emails throughout the day with natural delays
Here’s a good starting point for daily sending:
Start with 15–20 emails per day, then gradually increase by 3-5 emails/day, with a delay of 300-450 seconds:
Final tips before the start
Always include an opt-out option in your emails.
Giving recipients an easy way to unsubscribe isn’t just a best practice - it’s essential for keeping your emails out of the spam folder.
A clear and visible opt-out link:
Lowers the chances of recipients marking your emails as spam
Helps maintain a strong and healthy sender reputation
Builds trust and shows respect for your audience
Learn more about different opt-out options here:
Use unique content across domains
Avoid using the same email content across different domains.
If one domain gets flagged, sending the same emails from other domains can also put their sending reputation at risk.
The more unique and relevant your email feels to each recipient, the better your deliverability will be
Analyze your performance across different email providers
If you notice a drop in performance metrics, check the stats by provider. If one provider shows lower results, consider reducing your sending volume to that email provider.
For overall deliverability declines, use inbox placement testing tools to identify potential issues.