What is a hard bounce?
Definition
What is a hard bounce?
A hard bounce is an email that permanently fails to deliver. The recipient's server rejects the message outright, and no amount of retrying will change the outcome. Common causes include invalid email addresses, nonexistent domains, and server-level blocks.
When an email hard bounces, most email platforms automatically remove that address from future sends. This protects your sender reputation and keeps your deliverability rates healthy.
Hard bounce vs. soft bounce
Not all bounces are permanent. A soft bounce signals a temporary problem: the recipient's inbox is full, their server is down, or your message exceeded size limits. Email servers typically retry soft bounces several times before giving up.
Hard bounces are different. They indicate a fundamental issue with the address itself. Here's how to tell them apart:
| Hard bounce | Soft bounce |
|---|---|
| Permanent failure | Temporary failure |
| Invalid address, blocked domain, or nonexistent mailbox | Full inbox, server timeout, or message too large |
| Address should be removed immediately | Address may still be valid |
| Damages sender reputation if ignored | Can become a hard bounce after repeated failures |
Why emails hard bounce
Several issues trigger permanent delivery failures:
The email address doesn't exist. A typo during signup, a deleted account, or a made-up address all produce the same result. The server looks for the mailbox, finds nothing, and rejects your message.
The domain is invalid. If the part after the @ symbol points to a domain that doesn't exist or has expired, there's nowhere for the email to go.
The recipient's server blocked you. Some servers reject messages from senders with poor authentication, low reputation scores, or content that triggers spam filters. Unlike soft bounces from temporary spam filtering, these blocks are often permanent.
How hard bounces hurt your email program
Every hard bounce chips away at your sender reputation. Mailbox providers like Gmail and Outlook track how often your emails fail to deliver. A pattern of bounces signals that you're not maintaining your list, which makes providers more likely to filter your messages to spam or block them entirely.
The damage compounds over time. High bounce rates lead to lower inbox placement, which leads to lower engagement, which further erodes your reputation. It's a cycle that gets harder to break the longer it continues.
How to prevent hard bounces
You can't eliminate bounces entirely, but you can keep them rare.
Use double opt-in for new subscribers. When someone signs up, send a confirmation email they must click before joining your list. This catches typos and fake addresses before they cause problems.
Clean your list regularly. Remove addresses that haven't engaged in months. Use a verification service to catch invalid addresses before you send. ActiveCampaign integrates with tools like QuickEmailVerification to automate this process.
Authenticate your sending domain. Set up SPF, DKIM, and DMARC records so receiving servers can verify your emails are legitimate. Proper authentication reduces the chance of being blocked.
Monitor your bounce rate. Industry benchmarks suggest keeping your bounce rate below 2%. If you're consistently higher, investigate the source, whether it's a bad list segment, a problematic signup form, or an authentication issue.
What to do when an email hard bounces
When ActiveCampaign detects a hard bounce, the address is automatically suppressed from future campaigns. You don't need to manually remove it.
If you believe a valid address bounced incorrectly, say a contact confirms they're still using that email, you can investigate further. Sometimes strict spam filters cause legitimate addresses to bounce. In those cases, ask the recipient to add your sending address to their allowlist, then unsuppress the contact in your account.
For a deeper dive into maintaining list health, see our guide to email list cleaning.
FAQs
What's an acceptable hard bounce rate?
Aim for under 2% per campaign. Anything consistently higher suggests list quality issues that need attention.
Will removing hard bounces hurt my list size?
Your list may shrink, but your results will improve. Sending to valid, engaged addresses produces better open rates, click rates, and conversions than blasting a bloated list full of dead ends.
Can a hard bounce become deliverable again?
Rarely. If someone recreates a previously deleted email address, it might work, but this is uncommon. Treat hard bounces as permanent unless you have specific evidence otherwise.
How do hard bounces affect my sender reputation?
Mailbox providers interpret frequent bounces as a sign of poor list hygiene. This lowers your reputation score, making it harder for even valid emails to reach the inbox.
Ready to protect your deliverability and reach more of the right people? Start your free ActiveCampaign trial and see how automated list management keeps your email program healthy.
