What is an Email Bounce?
When an email cannot be delivered to a recipient, you'll see a "bounce" status with a reason explaining why the delivery failed. This guide explains the most common bounce errors and what you can do about them.
An email bounce occurs when an email cannot be delivered to the recipient's inbox. Bounces are classified into two types:
Hard Bounce: A permanent delivery failure (e.g., the email address doesn't exist). These emails will never be delivered.
Soft Bounce: A temporary delivery failure (e.g., mailbox full). These may succeed if re-tried later.
Common Bounce Errors
Invalid Email Address / User Not Found
What you'll see:
550 5.1.1 User Unknown
550 Mailbox not found
550 No Such User Here
552 Requested mail action aborted, mailbox not found
The email account that you tried to reach does not exist
What it means:
The email address doesn't exist on the recipient's mail server. This is usually because:
The email address was typed incorrectly
The person no longer works at that company
The email account was deleted
What you can do:
Double-check the email address for typos
Contact the customer by phone to confirm their current email address
Check if you have an alternate email address on file
Mailbox Full
What you'll see:
552 5.2.2 mailbox is full
Quota exceeded (mailbox for user is full)
This message could not be delivered because the recipient's mailbox is full
What it means:
The recipient's email inbox has reached its storage limit and cannot accept new messages.
What you can do:
- Wait a day or two and try resending the email
- Contact the recipient by phone to let them know their mailbox is full
- Use an alternate email address if available
Domain or DNS Issues
What you'll see:
- Unable to get MX info
- Failed to get IPs from PTR record
- The IP address resolved to a BOGON address
What it means:
The recipient's email domain is not properly configured to receive email. This can happen when:
The domain name has expired
The domain doesn't have email set up
The company has gone out of business
What you can do:
Verify the domain looks correct (no typos in the part after the @ symbol)
Contact the customer by phone to get an updated email address
Check if the company/domain still exists
Policy or Security Rejection
What you'll see:
550 5.7.1 Command rejected
550 5.7.1 Relaying denied
550 5.7.0 Local Policy Violation
Your organization does not allow external forwarding
What it means:
The recipient's email server is blocking the message due to their security settings. This is common with corporate email systems that have strict filtering rules.
What you can do:
Ask the recipient to whitelist emails from CheckCherry
Have the recipient check their spam/junk folder
Use an alternate email address (personal email may work if corporate is blocking)
Contact the recipient's IT department if this is a business client
DMARC / SPF Policy Rejection
What you'll see:
550 5.7.23 Sender Policy Framework violation
Your message was rejected due to DMARC policy
What it means:
This typically happens when the recipient has email forwarding set up (e.g., their old email address forwards to a new one). Modern email security checks can fail when emails are forwarded, causing the message to be rejected.
The forwarding server should use protocols like ARC (Authenticated Received Chain) to preserve the original authentication, but not all email providers have this configured correctly.
What you can do:
Ask the recipient for their direct email address instead of a forwarded alias
Have them check if the email landed in spam at their final destination
Suggest the recipient contact their email provider or IT department about enabling ARC for forwarding
Connection Timeout
What you'll see:
i/o timeout
connection timed out
error dialing remote address
What it means:
Our email server couldn't connect to the recipient's email server. This is usually a temporary issue on the recipient's end.
What you can do:
Wait and try again later—this often resolves itself
If it persists, the recipient's email server may be having extended issues
Contact the recipient by phone if the email is time-sensitive
Frequently Asked Questions
Q: Will the system automatically retry bounced emails?
A: Soft bounces (like mailbox full or timeouts) may be retried automatically. Hard bounces (like invalid addresses) will not be retried.
Q: How can I prevent bounces?
A: The best way to prevent bounces is to confirm email addresses with your customers when they book. Ask them to double-check the spelling.
Q: A customer says they didn't receive my email but I don't see a bounce. What happened?
A: The email may have been delivered but filtered to their spam or junk folder. Ask them to check there and add your sending address to their contacts.
Need More Help?
If you're experiencing a high number of bounces or have questions about a specific bounce error not listed here, chat with support from within your account.
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