550 5.1.1 Recipient address rejected: User unknown in virtual alias table;
554 5.7.1 Service unavailable; Client host X.X.X.X blocked using zen.spamhaus.org; This is the error message that is received of the IP address of the sender is listed at zen.spamhaus.org For further details, please check http://www.spamhaus.org/zen OR check http://www.spamhaus.org/query/bl?ip=<your_ipaddress> and contact zen.spamhaus.org to get the IP De-listed.
550 5.7.1 : Helo command rejected: You aren't localhost. 550 5.7.1 : Helo command rejected: You aren't localhost.localdomain. 550 5.7.1 : Helo command rejected: You are not me</XXX@XX.COM></XXX@XX.COM></XXX@XX.COM> Our servers do not accept SMTP HELO command as HELO localhost or HELO localhost.localdomain or HELO . We accept HELO from a valid Domain Name or your computer name which is other than your domain name. Please check with your ISP or Mail administrator for this issue.
554 5.7.1 : Relay access denied;</XXXX@XXXX.XXX> There are couple of reasons for this error while sending an email
551 5.7.1 The message was rejected due to classification as Virus,Spam or high bulk ratio. Please see http://support.mailhostbox.com/email-administrators-guide/error-codes This is a bounce back message that you receive when an email is classified as spam while sending out. If you feel that a genuine email is rejected as spam, you need to send the same email with the full headers and the content to our support team. That email in question will be reviewed manually.
530 5.7.0 Recipient address rejected: Authentication Required.</USER@DOMAIN.COM> This error comes when your sending mails to remote domain without using smtp authentication.
550 5.4.5 Recipient address rejected: Hourly domain sending quota exceeded</USER@DOMAIN.COM> This is the error message that you get if your domain name exceeds the hourly quota set for the domain name. Here, the term 'hour' refers to the last 60 minutes.
550 5.4.6 Recipient address rejected: Hourly sending quota exceeded</USER@DOMAIN.COM> This is the error message that you get if the user (that particular email address) exceeds the hourly quota set. Here, the term 'hour' refers to the last 60 minutes.
553 5.7.1 Sender address rejected: not owned by user firstname.lastname@example.org</USER1@DOMAIN.COM> This is the error message that is received when you are trying to send an email as a different user. This error message is seen by the users who are using Exchange servers with our system.
You need to add an identity for the same in the webmail. For example,
554 5.7.1 : Recipient address rejected: USER IS SUSPENDED </XXX@XX.COM> This error comes if user is suspended in Control Panel.
522 5.7.1 : Recipient address rejected: Requested mail action aborted: exceeded storage allocation</XXX@XX.COM> This error comes if the user is overquota.
554 5.7.1 : Sender address rejected: Access denied.</XXX@XX.COM> This error comes when the sender address is blocked on our server. Generally this is done if spam has originated from this user.
450 4.7.1 Client host rejected: cannot find your reverse hostname Our inbound servers require reverse hostname for the sender server to be present in order to accept the email. You need to contact the reverse hostname's email admin to add the rDNS to into his server.
450 4.7.1 : Recipient address rejected: Policy Rejection- Quota Exceeded</XXX@XX.COM> This error comes from our incoming mail server if user is receiving excessive amounts of mails.
450 4.7.1 Recipient address rejected: Access denied. This occurs when the recipient address is invalid. i.e., not in form of user@domainname OR if the Recipient address is blocked on server.
451 4.3.5 Server configuration problem - try again later; 451 4.7.1 Service unavailable - try again later; This error most likely occurs if there is a configration error with our servers. If you encounter any of the above messages, please contact our support helpdesk with the details.
452 4.5.3 Error: too many recipients The error message is encountered when the user is exceeding the limit of more than 30 recipients in an email. The list of recipients is inclusive of To,Cc and Bcc. If you encounter the above error, reduce the number of recipients in the email and try again.