Email bounces occur when your messages can't be delivered to recipients. Understanding why bounces happen and how to prevent them is critical for maintaining sender reputation and deliverability.
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When an email bounces, you'll receive a bounce report in your inbox detailing why delivery failed. These reports typically include error codes and explanations from the recipient's email server.
Two Types of Bounces
Hard Bounces(Permanent Failures)
Hard bounces seriously damage your domain health and sender reputation. Email can't be delivered because:
Email is invalid or doesn't exist
Domain doesn't exist
Email was deleted/deactivated
Typo in email address
How to prevent:
Use email verification tools to validate addresses before uploading
Soft Bounces (Temporary Failures)
A soft bounce occurs when the recipient's email address is valid, but the message can't be delivered due to temporary issues.
Key difference from hard bounces: Soft bounces are temporary and may resolve themselves. The same email might be deliverable later.
Common Soft Bounce Causes
Recipient's Inbox Is Full: The recipient's mailbox has reached its storage limit, preventing new messages from being received.
Server Issues: The recipient's email server is temporarily unavailable due to maintenance, overload, or other technical problems.
Poor sender reputation: Issues with DNS records, domain setup, or sending behavior can lead to rejection
Spam Filters: Your emails may be filtered out due to content, keywords, or sender reputation, such as heavy HTML templates, signatures with lots of links/icons, or aggressive sales language.
Copy repetition: When thousands of emails look nearly identical, providers may throttle or defer them as pattern-based outreach.
Links in Step 1: The first email is where providers are strictest. Links in Step 1 can increase soft bounces, especially when combined with repetitive copy.
Sending Too Much, Too Fast: Even with a good setup, sudden volume increases can cause throttling, such as ramping too quickly day over day, large batches in a short time window, or identical emails sent from many inboxes simultaneously
Catch-all domains: Some domains accept all emails initially but reject them later
Blocked Email Address: The recipient's email server may have blocked your email address or domain. Some organizations have strict email policies that block unsolicited emails from unknown senders, causing these messages to bounce.
How to Fix Bounces
Review the bounce report in your mailbox for detailed reasons. To view bounce error messages directly in Instantly without logging into your original mailbox, you can enable this setting:
Go to Preferences
Enable the 'Save undelivered emails in Unibox' option
Once enabled, the bounce notifications you receive in the connected email account will be synced in Unibox
Checklists Before Resuming Your Campaign
Pause your campaigns and allow only the warm-up to run for a few weeks
Use Inbox Placement feature to check sender reputation
Check DNS records (SPF, DKIM, DMARC) are properly configured
Review recent campaign content for spam triggers
Avoid images or links in Step 1
Clean your lead list to email only verified leads
After reviewing the above, resume your campaign and monitor for any improvements in bounce rates. Consider lowering your cold outreach volume and gradually increasing the sending limit.