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.
Hard Bounces
A hard bounce happens when the email address you're trying to send an email to is no longer valid or has never existed. It is important from a domain health and deliverability perspective that you avoid as many hard bounces as possible.
Hard bounces can be avoided by cleaning your lead lists. Use email verification tools to validate addresses before adding them to campaigns. Learn how to verify leads.
Soft Bounces
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
Attachments Triggering Spam Filters: Email attachments can trigger security filters, especially with certain file types or from unknown senders. Send emails in plain text with no attachments for the initial email.
Spam Words in Email Content: Certain words and phrases flag emails as spam, causing rejection by recipient servers. Avoid using special characters, non-Latin letters, and spam-triggering or overly sales-focused words such as 'earn $', 'credit card', and 'FREE', etc.
Recipient's Inbox Is Full: The recipient's mailbox has reached storage capacity and can't accept new messages.
Low Sender Reputation: If your domain or IP has poor reputation, some email servers will reject your messages even if the recipient address is valid.
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.