Hosting users receive an SMTP (Simple Mail Transfer Protocol) error when the recipient’s mail server blocks the emails they send. The list of known SMTP 550 messages clearly shows that there is no one-size-fits-all solution to this problem. It is important to respond appropriately to the specific cause of each error message. Below, we list the main error messages you may receive, along with explanations and advice on how to resolve the problem.

Error “550 Sender verification failed”

This error message appears if the sender’s email account does not exist, or if the domain’s MX records are configured incorrectly in cPanel.

Solution:

• Please ensure that the email account used to send messages actually exists in your cPanel account, and that you are using the correct username and password for SMTP authentication.
• In the cPanel > E-MAIL > Email Forwarding menu, select the ‘Remote Server’ option.
• Edit or create the MX records required for your remote email provider.
• Check and correct your SPF record.

Error “550 No such user here”

This error usually occurs when a sent email is rejected because the recipient’s email username cannot be found or the server is unavailable.

Solution:

• Please confirm with the recipient that they have the correct email address.
• Please try sending the email again in a few minutes or hours.

Error “550 Relay not permitted”

To protect users, every modern mail server maintains its own list of domains for which it processes emails. If your domain is not included on the mail server’s list, anyone attempting to send an email to it will receive a ‘550 Unauthorised Relay’ error message. This is not a particularly common problem, but it can occur, especially if you have recently changed your mail server.

Solution:

• In your email client, follow the settings required to connect to the outgoing SMTP server and select the option that requires password authentication.
• Use the same username and password for the incoming and outgoing servers.

Error “550 Mailbox quota exceeded”

You will receive the error message ‘550 Mailbox Quota Exceeded’ if you try to send an email to a recipient whose mailbox does not have enough space to store the message.

Solution:

• Errors will continue to occur until the recipient frees up space in their mailbox (by deleting emails and attachments or increasing their email quota).
• If others receive a ‘550 quota’ error when trying to send you an email, you will need to delete the emails and attachments from your inbox, or increase the quota for your email address.

Error “550 Outgoing mail has been suspended”

If you find that you are unable to send emails from your email account, it may be that our system has suspended it due to suspicious activity, because you have attempted to send a large number of messages or have received a large number of bounce messages.

This is simply an automatic protection mechanism designed to prevent the sending of unsolicited email (spam) caused by a virus on the device where the account has been configured to scan messages, or due to misuse.

Solution:

• To resolve this issue, please contact us by email or via a ticket.