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SMTP Error Codes

There are times that you may receive bounce mail entitled “Undelivered Mail Returned to Sender” after you have sent an email to your recipient.

Please kindly forward the error description to for further investigation.

The following are some common error messages that are included in the bounce mail for your reference.

SMTP Error 550

Sample descriptions:

  • Mailbox unavailable
  • Invalid recipient
  • No such user here
  • Relaying denied

Error 550 implicates that your mail server is unable to deliver email to the recipient due to his mailbox does not exist. Possible causes to this are: you have entered the wrong email address (spelling mistake), or the recipient account has been disabled and replaced with a new one, which you did not know.
It may also caused by a block from the recipient, by his spam filter.

To resolve this issue, you need to find out the correct email address and resend your mail, or contact the recipient to whitelist your email address on his mail server.

SMTP Error 552

Sample descriptions:

  • Over quota
  • The recipient’s mailbox has reached its maximum allowed size

Due to the recipient's mailbox is full, or his incoming email limit has exceeded, your email is not able to reach his mailbox.

Contact the recipient by other means to inform about the error.

SMTP Error 554

Sample descriptions:

  • Your IP address is listed in spam filter
  • Sending address not accepted due to spam filter

This error message is returned to you due to the recipient's email server believes that your email is a spam or your mail server is blacklisted.

Forward the error message to for further investigation.

faq/email/smtp_error_codes.txt · Last modified: 2022/03/07 11:36 by vikki