Posted by You did everything right. You ran your email list through a verification service. You removed the invalid addresses. Your list came back clean.
Then you sent your campaign. And emails still bounced.
This is frustrating, but it is entirely normal. Email verification dramatically reduces bounces, but it cannot eliminate them. There are factors beyond Verification that cause deliverable emails to bounce.
According to Mailchimp’s documentation, even addresses that previously received emails successfully can bounce due to temporary server issues, full mailboxes, or policy changes on the recipient’s end.
In this guide, you will learn precisely why verified emails bounce and what you can do about each cause. Understanding these factors helps you set realistic expectations and take the right corrective actions.
What Email Verification Can and Cannot Do
Email verification is robust, but it has limits. Understanding these limits helps you know what to expect.
What Verification Confirms
When you verify an email address, the verification service checks several things:
- Syntax validity: The email address is formatted correctly
- Domain existence: The domain has valid MX records and can receive email
- Mailbox existence: The specific mailbox exists on that domain (via SMTP check)
- Risk factors: Whether the address is disposable, role-based, or a known spam trap
What Verification Cannot Predict?
Verification tells you the state of an email address at the moment of Verification. It cannot predict:
- Future server outages on the recipient’s end
- Whether a mailbox will become full between Verification and sending
- Policy changes on the recipient’s mail server
- How your specific email content will be filtered
- Whether your sending IP or domain is temporarily blocked
This is why even a perfectly verified list will have some bounces. The goal is to minimize bounces, not eliminate them.
10 Reasons Verified Emails Still Bounce
Here are the most common reasons you see bounces even after Verification, along with what to do about each one.
1. Recipient Server Is Temporarily Down
What happens: The recipient’s email server is offline, overloaded, or under maintenance when your email arrives. The server cannot accept the message, so it bounces.
Bounce type: Soft bounce (temporary)
What to do: Most email service providers automatically retry soft bounces for 24 to 72 hours. If the bounce persists after multiple retries, the ESP will convert it to a hard bounce. Monitor these addresses, but do not remove them immediately after a single soft bounce.
2. Mailbox Is Full
What happens: The recipient’s inbox has exceeded its storage quota. The server rejects new messages until space is freed up.
Bounce type: Soft bounce initially, but can become a hard bounce if the mailbox stays full.
What to do: A full mailbox often indicates an inactive or abandoned account. According to HubSpot’s bounce documentation, if an address bounces repeatedly due to a full mailbox, it should eventually be treated as a hard bounce and removed.
3. Email Authentication Failure
What happens: Your email fails SPF, DKIM, or DMARC authentication checks. The recipient server rejects the message as a security precaution.
Bounce type: Hard bounce (policy rejection)
What to do: Check your domain authentication settings. Make sure SPF, DKIM, and DMARC are correctly configured for your sending domain. Use tools like Google Postmaster Tools or MXToolbox to diagnose authentication issues. This is a sender-side problem, not a list quality issue.
4. Content Triggered Spam Filters
What happens: Something in your email, such as the subject line, body content, links, or images, triggered the recipient server’s spam filter. The server rejects the message.
Bounce type: Hard bounce (content rejection)
What to do: Review your email content for spam triggers. Avoid excessive promotional language, too many exclamation points, suspicious links, or image-heavy emails with little text. Test your emails through spam-checking tools before sending to your whole list.
5. Your IP or Domain Is Blocklisted
What happens: Your sending IP address or domain appears on an email blocklist. Recipient servers that check these lists automatically reject your messages.
Bounce type: Hard bounce (blocked sender)
What to do: Check blocklist status using tools like MXToolbox or Spamhaus lookup. If you find your IP or domain on a list, follow the delisting process for that specific blocklist. Review your sending practices to identify what triggered the listing.
6. The Address Changed Between Verification and Sending
What happens: The email address was valid when you verified it, but something changed before you sent your campaign. The person left the company. The account was deleted. The domain expired.
Bounce type: Hard bounce (address no longer exists)
What to do: Minimize the gap between Verification and sending. If you verified your list months ago, verify again before your campaign. Email lists decay 22 to 30% annually, and even recent lists can have changes.
7. Email Size Exceeded Server Limits
What happens: Your email, including attachments and embedded images, exceeds the size limit set by the recipient’s mail server. Most servers limit incoming emails to 10 to 25 MB.
Bounce type: Hard bounce (message too large)
What to do: Compress images and avoid large attachments. Host files externally and link to them instead of attaching. Keep your total email size under 10 MB to be safe across all mail servers.
8. Recipient Server Has Strict Policies
What happens: Some corporate and government mail servers have stringent acceptance policies. They may require specific authentication, sender reputation thresholds, or manual allowlisting before accepting external emails.
Bounce type: Hard bounce (policy rejection)
What to do: If you consistently cannot reach addresses at a specific domain, it may require the recipient to allow your sending address. For important contacts, reach out through another channel and ask them to add you to their approved senders list.
9. Catch All Domain Delayed Bounce
What happens: Catch all domains accept all emails initially. But some configurations later bounce emails to nonexistent mailboxes after the initial acceptance. This creates a delayed bounce that Verification cannot predict.
Bounce type: Delayed hard bounce
What to do: Use AI scoring for catch-all addresses to identify which ones are likely to be active. Send to catch all addresses in small batches and monitor bounce rates closely. Remove addresses that bounce regardless of their verification status.
10. Email Forwarding Broke
What happens: The email address forwards to another account. The original address accepts the email (passing Verification), but the forwarding destination rejects it or no longer exists.
Bounce type: Delayed bounce (forwarding failure)
What to do: There is no way to detect forwarding issues before sending. When you receive these bounces, add the addresses to your suppression list. If a recipient reaches out about not receiving emails, ask them to check their forwarding configuration.
What Bounce Rate Should You Expect After Verification?
A verified list should have significantly fewer bounces than an unverified one. But some bounces are still regular.
Here is what to expect:
- Excellent: Under 0.5% bounce rate
- Good: 0.5% to 1% bounce rate
- Acceptable: 1% to 2% bounce rate
- Needs attention: Above 2% bounce rate
If your verified list bounces above 2%, something else is wrong. Check your sender authentication, review your content, and verify that your sending IP is not blocklisted.
If bounces are below 1%, your Verification is working well. The remaining bounces are likely due to temporary issues or factors outside your control.
Best Practices to Minimize Post Verification Bounces
Follow these practices to keep your bounce rate as low as possible:
Verify Close to Send Time
The longer the gap between Verification and sending, the more addresses will change. Verify your list within 7 days of sending for best results. If your list is extensive, verify it in batches close to each campaign.
Set Up Proper Authentication
Configure SPF, DKIM, and DMARC for your sending domain. Authentication failures cause bounces that have nothing to do with list quality. Many ESPs guide you through this setup, but verify that it is working correctly.
Monitor Your Sender Reputation
Use Google Postmaster Tools and similar services to monitor your domain reputation. A declining reputation can cause bounces and spam filtering even when sending to valid addresses.
Process Bounces Immediately
When an email bounces, remove hard bounces from your list immediately. For soft bounces, allow your ESP’s retry process to complete before taking action. If a soft bounce persists across three consecutive sends, treat it as a hard bounce.
Test Before Full Sends
Send to a small test segment first. If bounces are higher than expected, investigate before sending to your whole list. This limits the damage from content issues or authentication problems.
Frequently Asked Questions
Is it normal for verified emails to bounce?
Yes. Some bounces are normal even with a verified list. Verification confirms the address exists at the moment of Verification, but temporary server issues, policy changes, and other factors can cause bounces at send time. A bounce rate under 1% on a verified list is typical and acceptable.
How soon after Verification should I send?
Ideally, within 7 days. The fresher your Verification, the more accurate it will be. If you wait months between Verification and sending, account changes, job changes, and domain expirations will increase your bounce rate.
Should I remove soft bounces from my list?
Not immediately. Soft bounces are temporary issues. Most ESPs automatically retry soft bounces for 24 to 72 hours. Only remove an address if it soft bounces repeatedly across multiple campaigns. A good rule is three consecutive soft bounces before treating it as a hard bounce.
Can the same email address verify as valid, then bounce?
Yes. Verification checks if the mailbox exists and can receive email at that moment. But the recipient’s server can still reject your specific email due to content filters, sender reputation, authentication failures, or temporary issues. The address is valid, but delivery is blocked for other reasons.
My bounce rate increased. Is my verification service broken?
Probably not. If bounces increase suddenly, first check your sender authentication and reputation. Check if your IP or domain is blocklisted. Review your email content for spam triggers. List quality is only one factor in deliverability. A sudden increase usually points to sender-side issues rather than verification failures.
Keep Your Bounce Rate Low
Email verification is essential for healthy email marketing. It removes the addresses that will definitely bounce. But it cannot eliminate all bounces.
The remaining bounces come from factors outside Verification’s control: server issues, policy changes, authentication problems, and content filtering. Understanding these causes helps you take the proper corrective action.
Focus on what you can control. Verify your list close to send time. Set up proper authentication. Monitor your sender reputation. Process bounces quickly. Test before complete sends.
With these practices in place, you can keep your bounce rate under 1% and maintain a healthy sender reputation.
Need to verify your list before your next campaign? Try myEmailVerifier to remove invalid addresses and minimize your bounce rate. Clean lists mean better deliverability and a stronger sender reputation.
James P. is Digital Marketing Executive at MyEmailVerifier. He is an expert in Content Writing, Inbound marketing, and lead generation. James’s passion for learning about people led her to a career in marketing and social media, with an emphasis on his content creation.