Common bounce email errors and solutions

Message

Bounce Reason

Solution

spammed by local spam engine

The anti-spam system identified the email as spam and rejected it.

Bounce message: spammed by local spam engine

• 454 Transient reject by behaviour spam...

• 554 Reject by behaviour spam...

Rejected by the behavior-based anti-spam system

1. The sender's sending frequency or volume exceeds Alibaba Mail limits.

2. The sender's server IP address or domain name is on the blacklist of an anti-spam organization. The system has determined that the sender has a low reputation and is sending spam. To protect the Alibaba Mail system from malicious emails, the Alibaba Cloud server may reject emails from IP addresses or domains with low reputations.

• Bounce message: 454 Transient reject by behaviour spam

• Bounce message: 554 Reject by behaviour spam

502 Mailfrom account is a local account

This error occurs if you use a local client to send an email from an Alibaba Mail account to another Alibaba Mail account, but the outgoing mail server in your client is set to a proxy server or a server other than the one specified by Alibaba Mail. The correct outgoing mail server address is smtp.qiye.aliyun.com on port 25.

Bounce message: 502 Mailfrom account is a local account

503 Rcptto account isn’t a local account

1. The recipient uses Alibaba Mail, but the sender misspelled the recipient's email address.

2. The recipient previously used Alibaba Mail but has switched to a different email system. However, the system still has a record of the old email domain.

Bounce message: 503 RCPT account isn't a local account

504 The number of RCPT attempts has reached the maximum threshold

You have exceeded your sending limit.

Reduce the number of emails you send and try again the next day.

505 The total of RCPTs has reached the maximum threshold

The number of recipients for a single email exceeds the limit.

Send them separately. For more information, see Common Parameters for Standard Accounts.

510 The length of DATA content has reached the maximum threshold

The email body exceeds the character limit.

Reduce the content in the email body and send it again.

510 The length of Attachment has reached the maximum threshold

The size of the email attachment exceeds the maximum limit.

Please make any necessary adjustments before sending.

510 The number of attachments has reached the maximum threshold

The number of attachments exceeds the limit.

Reduce the number of attachments and send the email again.

526 Authentication failure

Authentication failed.

Bounce message: 526 Authentication failure

541 This account isn't allowed to send email

Outgoing emails are blocked because the account was used to send spam or was compromised.

What do I do if an Alibaba Mail employee account is blocked or frozen?

550 mailbox is full

The recipient's mailbox is full. Please ask the recipient to clear memory from their mailbox. You can then send the message again.

Bounce Message: 550 Mailbox is full

554 Reject by content spam

If an email is marked as spam, you can modify the content and resend it. Alternatively, you can submit a ticket that includes the sender address, recipient address, and the time it was sent for our support team to determine if the email was incorrectly flagged.

Bounce message: 554 Rejected due to spam content

Message

Bounce Reason

Solution

the mta server of ...(x.x.x.x) reply:...

An email is rejected by the recipient's server, often due to error semantics in the server's response.

For more information, refer to the semantics or consult the recipient's mailbox administrator or service provider.

Bounce message: the mta server of ... reply

User not found

Delivery failed because the recipient address is in an incorrect format or does not exist.

1. Check the recipient's address for errors, such as extra spaces or special characters.

2. Check if the recipient's MX record is configured correctly. If there is an invalid MX record, contact the recipient's email administrator.

3. Contact the recipient through other means to confirm the status of the mailbox. Check if it has expired, been disabled, or frozen.

User unknown, Invalid User, No exist

550 No such user

550 Mailbox not found

invalid address (#5.5.0)

550 Mail content denied

Dns, Host, Not found, Bad host, Domain, Unreachable

The domain name part of the address (the text after the @ sign) is invalid, or the domain name could not be resolved by DNS.

1. Verify that the recipient's address is correct and send the email again.

2. Use an email account from another email provider to send a test email to the recipient and see if it bounces.

Sorry, I couldn' t find any host named xxx (#5.1.2)

Quota exceeded

The recipient's mailbox is full, or the email size exceeds the recipient's server limits.

2. The email exceeds the recipient's maximum email size limit.

1. If the recipient's mailbox is full, see How to handle email reception failures in Alibaba Mail due to a full mailbox.

2. If the email exceeds the recipient's size limit for a single email, send it as an extra-large attachment.

mailbox is full

Quota exceed the hard limit for user

mail box space not enough

552 5.7.0 content and attachment content guidelines

Too large, Maximum fixed size

552 Message size exceeds fixed limit

Rejected, Not allowed, Message blocked

The email was rejected by the recipient's server, usually due to its anti-spam policy.

Contact the recipient and ask them to add your email address to their allowlist or contact their email administrator to determine the reason for rejection.

552 Error: content rejected, 553 Mail data refused

Black list, Spam, Spammers

The recipient's server identified the email as spam and rejected it.

The reason for rejection can vary. Analyze the specific bounce message from the recipient's server. We recommend optimizing the email content before trying again.

If the message is unclear, ask the recipient to contact their administrator or service provider for assistance.

Connection timed out, 554 delivery error

A network issue caused a timeout when connecting to the recipient's server, resulting in a delivery error.

This error can be caused by downtime on the recipient's mail server or poor network connectivity. Alibaba Mail automatically retries delivery to increase the success rate. You can also:

• Try to send the email again later.

• Contact the recipient through other means to confirm if their mail server is stable.

Error in command, Syntax error

The recipient's server did not recognize an SMTP command sent by your email client.

Try sending the email from a standard email client, such as Outlook or Foxmail, or send it directly from the web-based client.

553 Too many recipients in the mail, should less than 20

The email broadcast has too many recipients.

Send a separate email to this address, or reduce the number of recipients in a single email.

542 This account isn't allowed to receive email

Due to recipient address restrictions, you are not authorized to send emails to this account.

Contact the recipient through other means. Ask the recipient to contact their email administrator to grant authorization, and then try sending the email again.

422 ERR.LOGIN

An unknown error occurred while sending the email to the recipient's server.

1. Please contact your email provider for troubleshooting assistance.

2. A temporary error may have occurred due to an issue with the network provider (such as China Telecom, China Unicom, or China Mobile) during email transmission. Try sending the email again later.

550 failed to meet SPF requirements

The email failed the identity authentication check based on the recipient server's SPF policy.

Bounce message: spf check failed

spf check failed

521 5.2.1 AOL will not accept delivery of this message

The recipient's server rejected the email because the content is suspected of being bulk mail, spam, or promotional material.

We recommend that you send a simple test email to the recipient to see if it can be delivered successfully.

451 Temporary local problem - please try later

A temporary issue with the recipient's server caused the delivery to fail.

Try sending the email again later. If it still fails, contact the recipient through other means and ask them to report the issue to their email service provider.

451 4.3.2 Internal server error

The recipient's server rejected the email, causing the delivery to fail.

If you recently migrated your mailbox from another service provider and this error occurs when sending an email to a mailbox on the old system, it may be an SMTP Authentication issue. We recommend contacting your previous provider to unregister the domain name. If the domain is not unregistered, email delivery between the two systems will be affected.

550 5.7.1 Service unavailable; Client host [x.x.x.x] blocked using Trend Micro RBL+

The sender's outgoing IP address is on the blacklist of the recipient's anti-spam system.

Please ask the recipient to contact their mailbox administrator or service provider to allow emails from you.

Recipient address rejected: User unknown in virtual mailbox table (in reply to RCPT TO command)

The recipient's email address was not found on their server system.

Verify the accuracy of the recipient's email address and try sending it again.

• 550 Sender domain is a local domain.

• 550 Connection denied

• 550 Mail is rejected by recipients.

• 550 Mailbox unavailable or access denied

• 501 Bad address syntax

• 552 Message too large

• 550 Mailbox not found

• 550 Mail content denied

• 550 Ip frequency limited

• 550 Domain frequency limited

• 550 Sender frequency limited

• 550 Connection frequency limited

The recipient's server returned a bounce message. For the specific reason, see the explanation from the recipient's server.

https://open.work.weixin.qq.com/help2/pc/20038?person_id=1&id=20022

421 Service not available, closing transmission channel

Service or network is abnormal.

Try sending a test email later.

524 username or password is NULL

Incorrect account or password.

Verify that the account and password are correct, and then try sending the email again.

523 cipher text is invalid base64 format

Incorrect encoding.

Adjust the encoding format and try sending the email again.

450 "MAIL FROM" mailbox unavailable

Incorrect sender address.

Please check the recipient's email address and try again.

552 "RCPT TO" mailbox unavailable

Invalid recipient address.

Confirm that the recipient's account is in a normal state and can receive emails.

451 Requested action aborted: local error in processing

Abnormal recipient server.

Check your local terminal for any issues. Try restarting the service and sending again.

550 failed to meet SPF requirements

SPF check failed.

xxxx

551 virus infected mail rejected

The email may contain a trojan horse or virus.

Scan the email for viruses and then send it again.

534 Message is too long

The email body exceeds the character limit.

Reduce the content in the email body and send it again.

521 5.2.1 AOL will not accept delivery of this message

The recipient's server rejected this email.

Contact the recipient's email service provider for help.

451 Requested action aborted: local error in processing

You can check your local terminal for issues.

You can restart the service and resend.

400 Temporary failure

Connection failed.

You can try to send again.

551 virus infected mail rejected

The email contains a virus.

Please correct the email body and retry the delivery.

resolving by dns failed

1. Incorrect recipient address.

2. The recipient's MX server is abnormal.

1. Check if the recipient's address is incorrect.

2. Contact the recipient to confirm that their domain's MX record exists and points to the correct server. If the recipient's domain exists, try sending the email again later.

57 This email is rejected. It contains keywords rejected by the antispam content filter

The email content triggered a keyword in the recipient's anti-spam system.

Adjust the email content and try sending it again.

521 5.2.1 : AOL will not accept delivery of this message

The recipient's server rejected the email because the content is suspected of being bulk mail, spam, or promotional material.

We recommend that you send a simple test email to the recipient to see if it can be delivered successfully.

451 Temporary local problem - please try later

A temporary issue with the recipient's server caused the delivery to fail.

Try sending the email again. If it fails, contact the recipient's email service provider for confirmation.

550 Message is too large /Too large/Maximum fixed size/ 552 Message size exceeds fixed limit

The email is too large and exceeds the recipient's maximum size limit for a single email.

Split the email into smaller parts and send them separately.

550 5.7.1 Service unavailable; Client host [x.x.x.x] blocked using Trend Micro RBL+

The sender's outgoing IP address is on the blacklist of the recipient's anti-spam system.

Submit a ticket to your email service provider to request removal from the blacklist.

Recipient address rejected: User unknown in virtual mailbox table (in reply to RCPT TO command)

The recipient's email address was not found on their server system.

Verify the accuracy of the recipient's email address and try sending it again.

Email service provider

Bounce code description

Tencent Mail

https://open.work.weixin.qq.com/help2/pc/20038?person_id=1&id=20022

NetEase Mail

https://qiye.163.com/help/l-9.html

263 Mail

https://www.263.net/263/helpcenter/mailbounce/20150906/842.html

Gmail

https://support.google.com/a/answer/3726730

Microsoft mailboxes (such as @hotmail.com, @live.com, @live.cn, and @outlook.com)

• https://mail.live.com/mail/troubleshooting.aspx#errors

• https://learn.microsoft.com/zh-cn/exchange/troubleshoot/email-delivery/ndr/non-delivery-reports-in-exchange-online