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Check if an email address will bounce, before you send

Validate any email address instantly. Catch bad addresses, disposable inboxes, and dead domains in seconds.

4.7 /5 based on 2,111 reviews | GDPR Compliant

Why Gmail & Outlook hate hard bounces

Unlike spam complaints, hard bounces are technical failures that ISPs interpret as "you don't know who you're emailing." This triggers automatic penalties.
Our bounce checker finds these landmines before you step on them.
  • > 2% Bounce Rate: Your emails start landing in the Promotions tab or get throttled.
  • > 5% Bounce Rate: Your domain is flagged. Most emails go straight to Spam.
  • > 10% Bounce Rate: Your IP is blacklisted. Game over.

We check everything that causes a hard bounce

Most tools just guess. We perform real-time server handshakes to ensure 100% deliverability safety.

Verify your emails
SMTP handshake check

SMTP handshake check

We securely ping the mail server to ask if the mailbox exists. If the server says "User Unknown," we flag it as a hard bounce instantly.

Domain health check

Domain health check

We verify MX records and DNS entries. If a domain is expired or misconfigured, emails sent there will always bounce. We catch them first.

Spamtrap detection

Spamtrap detection

Hitting a spamtrap can blacklist your domain forever. Our database identifies these hidden traps so you never accidentally email them.

Catch-all server check

Catch-all server check

Some servers accept all emails to hide valid addresses. We identify these risky domains so you can segment them safely instead of risking a bounce.

Temporary email block

Temporary email block

Addresses from free trials or temp services (like Mailinator) are useless for long-term outreach. We remove them to keep your list clean.

Syntax & duplicate clean

Syntax & duplicate clean

We fix typos, correct formatting errors, and remove duplicate entries automatically. A clean list starts with perfect data hygiene.

Devon
Our bounce rate was at 8%. We were about to lose our main domain. Seller's free checker helped us identify the bad segment. Within 2 weeks, we were back in the primary inbox.
DevonMarketing manager

Compare traditional manual cleaning vs. Selleaser’s automated bounce checker

See why top teams switched from risky manual tests to Selleaser’s automated bounce protection.

Verify your emails
Traditional manual checks
Spend hours testing emails manually
High risk of blacklisting from test sends
Miss spam traps and hidden blacklists
Guess which addresses are catch-alls
Waste budget on emails that never arrive
Juggle spreadsheets to track bounces
Selleaser’s bounce checker
Verify 10,000+ emails in <5 minutes
Zero risk to your sender reputation
Detect spam traps before they hurt you
Identify catch-alls with precision
Save 40% on ESP costs instantly
Auto-segmented clean lists ready to use

When to run a bounce check

Critical moments where verification protects your sender reputation and prevents blacklisting.
Start free bounce check

Before a big launch

Don't let a 5% bounce rate kill your product announcement or fundraising email. Verify your list first to ensure maximum inbox placement when it matters most.

After buying a list

Purchased leads are often old, fake, or full of hard bounces. Running an independent bounce check before your first send prevents immediate blacklisting and wasted budget.

When open rates drop

A sudden decline in opens usually means your list has decayed or emails are landing in spam. Clean your list to recover visibility and restore engagement metrics.

Migrating ESPs

New providers like HubSpot or Mailchimp have strict bounce limits. Clean your list before importing to avoid account suspension and start with a pristine sender score.

Hard bounce vs soft bounce

Not all bounces are equal. A soft bounce is temporary—caused by a full inbox or a busy server. Emails usually get delivered later. A hard bounce is permanent. It means the address doesn't exist, the domain is expired, or the server blocked you. Hard bounces are the real threat. They signal to Gmail and Outlook that your list is outdated, directly triggering spam filters and lowering your sender score. Always remove hard bounces immediately.

How to recover your sender score after high bounces

If your bounce rate spikes, don't panic—but act fast. First, pause all campaigns to prevent further damage. Second, run a full list verification to isolate and delete every hard-bouncing address. Third, warm up your domain by sending low-volume, highly engaged emails to your most active subscribers. Consistent engagement tells ISPs you're legitimate. Within 2–4 weeks of clean sending, your sender score will recover. Prevention is always cheaper than recovery.

Spam traps the silent killers of email campaigns

A spam trap is a fake email address created by ISPs and blacklist operators specifically to catch spammers. They are never used by real people and are hidden across the web. If you send to a spam trap, you don't just get a bounce—you get flagged as a spammer instantly. Unlike bounces, spam traps can blacklist your entire domain permanently. The only way to avoid them is through proactive list hygiene and verification before every major send.

From bounce protection to revenue generation

Cleaning bounces is just the foundation. Build on it.

Eliminate hard bounces

Remove invalid emails that damage your sender score before they cause harm. Protect your domain reputation from day one.

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Add data to your leads

We find and add missing data like name, job title, company, and LinkedIn profile to your verified contacts.

Scan your list
Eliminate hard bounces

Remove invalid emails that damage your sender score before they cause harm. Protect your domain reputation from day one.

Scan your list

Frequently asked questions

What is a hard bounce and why does it matter?

A hard bounce is a permanent delivery failure—usually because the email address doesn't exist, the domain expired, or the server blocked you. Unlike soft bounces, hard bounces signal to Gmail and Outlook that your list is outdated. Too many hard bounces can blacklist your domain and kill your deliverability.

How does a bounce email checker work?

We perform a secure SMTP handshake with the receiving mail server to ask if the mailbox exists—without sending a real email. We also check domain health, MX records, spam traps, and catch-all patterns. The result: a clean list with zero risk to your sender reputation.

Will checking for bounces hurt my sender score?

Never. Our verification process pings the mail server technically—no messages are delivered, no recipients are notified. Your sender reputation stays completely protected throughout the check.

What bounce rate is considered dangerous?

Under 2% is healthy. Between 2-5%, ISPs start throttling your emails. Above 5%, your domain gets flagged and most emails land in spam. Above 10%, you risk permanent blacklisting. Run a bounce check before you hit these thresholds.

Can a verified email still bounce later?

Rarely, but yes. Mailboxes can be deleted, domains can expire, or servers can change policies after verification. That's why we recommend quarterly hygiene checks for active lists—and real-time verification for new signups.

What's the difference between hard and soft bounces?

A soft bounce is temporary (full inbox, server timeout). Emails usually get delivered later. A hard bounce is permanent (invalid address, dead domain). Hard bounces are the real threat—they directly damage your sender score and trigger spam filters. Always remove them immediately.

How do I fix a high bounce rate?

First, pause all campaigns to prevent further damage. Second, run a full bounce check to isolate and delete every hard-bouncing address. Third, warm up your domain by sending low-volume, highly engaged emails to active subscribers. Within 2-4 weeks of clean sending, your sender score will recover.

What are spam traps and how do I avoid them?

Spam traps are fake email addresses created by ISPs to catch spammers. They never belong to real people. If you send to one, you get flagged instantly—often with permanent domain blacklisting. The only way to avoid them is through proactive list hygiene and verification before every major send.

Can I check for bounces in bulk?

Yes. Upload a CSV, Excel file, or connect your CRM to verify thousands of emails at once. Our bulk bounce checker processes lists of any size and returns a clean, segmented file with valid, risky, and invalid addresses clearly labeled.

Protect your domain before your next send

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