What is a bounce reason?
A bounce reason is the message returned by the recipient’s email server when it cannot deliver an email.
Some reasons are easy to understand:
Email address does not exist.
Others are technical:
550 5.1.1 User unknown.
Both examples usually mean the receiving server could not find the recipient.
If you are not familiar with hard and soft bounces, start with Email Bounces in GlassHive.
Where does the bounce reason come from?
The recipient’s email server creates the bounce reason.
GlassHive records the information it receives, but GlassHive does not control how the other server writes the message.
Because every server is different:
Some reasons are very clear
Some include only a code
Some include several possible causes
Some are incomplete
A valid address can sometimes be rejected because of security or reputation rules
Where can I find bounce reasons in GlassHive?
From a campaign
Go to Marketing.
Select Email Marketing.
Open Campaigns.
Select the Sent section.
Open the campaign by clicking the hyperlinked name of the campaign.
Sort or filter by "Bounced"
Open the bounced contact's profile page by clicking on the hyperlinked name of the contact.
Navigate to the Activities tab of the contact
Locate and review the message or SMTP code returned by the recipient server for the email activity in question.
From Email Health Reports
Go to Reports.
Open Email Health.
Review the bounce rate.
Scroll all the way down to review all bounce reasons for all hard bounced contacts.
What is an SMTP code?
SMTP stands for Simple Mail Transfer Protocol. Email servers use SMTP to send messages and report delivery problems.
You do not need to understand every part of the code.
In general:
Codes beginning with 4 often describe a temporary problem
Codes beginning with 5 often describe a permanent rejection
The text after the code usually gives the most useful information. Typically, a copy/paste of the SMTP code and following message into a search engine will provide more information on the code and what can be done to remedy the issue.
Common bounce reasons
“User unknown,” “recipient not found,” or “mailbox does not exist”
The address probably does not exist.
What to do:
Check for typing mistakes
Confirm the address with the contact
Remove the address when you cannot confirm it
Do not upload it again unchanged
This is normally treated as a hard bounce.
“Domain not found” or “no such domain”
The part after the @ may be wrong or may no longer exist.
Example:
person@compnay.com instead of person@company.com
What to do:
Check the spelling
Confirm the company’s current domain
Do not guess at a replacement
Remove the contact if the correct address cannot be confirmed
“Mailbox full”
The inbox may be real but does not have room for another message.
What to do:
Wait before trying again
Monitor whether the problem continues
Stop marketing to the address if it repeatedly fails
Contact the person another way when appropriate
This is normally a soft bounce.
“Server temporarily unavailable” or “try again later”
The receiving server may be offline, busy, or delaying messages.
What to do:
Monitor the address
Check whether many people at the same company are affected
Review later campaign results
Investigate if the same server keeps rejecting messages
“Message too large”
The receiving server rejected the size of the email.
What to do:
Reduce image sizes
Remove large attachments
Link to files instead of attaching them
Simplify the campaign
“Blocked,” “rejected,” or “access denied”
The server refused the message.
Possible causes include:
Poor sender reputation
Spam-like content
Missing authentication
A domain or IP block
The recipient company’s security policy
A large amount of email being sent too quickly
What to do:
Check DKIM and DMARC
Review your bounce rate
Review the campaign content
Check the list source
Look for a blocklist name or help link in the message
Stop sending to the list if many contacts are affected
See Why Is My GlassHive Account Suspended? if the account has been suspended.
“Authentication failed,” “DKIM failed,” or “DMARC failed”
The receiving server could not confirm that the message was authorized.
What to do:
Go to your GlassHive email-authentication settings
Confirm that DKIM is active
Review your DNS records
Ask your DNS administrator or IT provider to check the setup
Add or correct DMARC where needed
See Setting Up Your DKIM.
“Spam,” “policy rejection,” or “message content rejected”
The receiving system believes the message or sender creates a risk.
Possible causes include:
The recipient did not expect the message
The sender has a poor reputation
The list contains risky contacts
The message includes suspicious links
The subject or sender information is misleading
The domain is not authenticated
What to do:
Stop sending to the list
Review where the contacts came from
Clean the full list
Check the sender information and subject line
Remove suspicious or unnecessary links
Confirm authentication
“Rate limited,” “too many messages,” or “temporarily deferred”
The receiving server may believe too much email arrived in a short period.
What to do:
Reduce the sending volume
Send to your most engaged contacts first
Warm up a new domain and sending combination
Avoid launching a large cold campaign
What if I know the address is valid?
A real address can still bounce.
Possible reasons include:
The company blocks unfamiliar senders
The mailbox is full
The server is temporarily unavailable
Your message failed authentication
Your domain or sending IP has a poor reputation
The company uses strict security filters
Read and research the complete reason before deciding what to do.
When possible, contact the recipient through another channel and ask their IT team to review the rejection or allow your company’s domain.
What if many contacts bounce at once?
Stop sending to the list.
Check:
The total bounce rate
Whether the list was recently imported
Whether the list is old
Whether it was purchased or supplied by another party
Whether many addresses share the same domain
Whether the message mentions blocking or spam
Whether DKIM is set up
A high number of bounces can quickly lead to an account suspension.
When should I contact GlassHive Support?
Contact Support when:
Your bounce rate is 2% or higher
Your account is suspended
Many addresses that you believe are valid bounced
The message mentions a blocklist
Many recipients at the same company are affected
You cannot understand the returned message
You completed an account-wide cleanup and need reinstatement review
Include:
The campaign name
The date sent
Example affected contacts
The complete bounce reason
Any SMTP code
A screenshot when available