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When sending an e-mail, sometimes you may find that it has been returned to your mailbox without reaching the recipient, indicating an error. Here is the meaning of the most common error messages you may receive:
All error codes beginning with 550 indicate that your email has been returned by the destination server.
It is important to note that more detailed information is provided in the body of the message, so it is always useful to read its contents in full.
This error indicates that the destination server does not accept your email. Although the message itself does not provide any further information, the main reason is usually a block.
If possible, you should contact the recipient to unblock your email account or domain, or to ask your provider to give you more details.
The error indicates that the email account or domain entered as recipient does not exist.
You should check the address you have entered for typos, spaces between characters or incorrect punctuation.
There are 2 different scenarios for this error:
In both cases, you should contact the recipient so that they can correct this behavior.
This error code indicates that the destination server does not accept any email from any account associated with your domain name.
The main cause usually refers to an incorrect configuration in the DNS zone or a DNS propagation in process.
You can check the DNS configuration of your service by following this link:
The error code indicates that the e-mail was rejected because it exceeded the size defined by the destination server.
The main cause is usually the attached files. You can try to compress them or split them into separate messages.
The error code indicates that the email has been rejected due to a problem or a security policy on the destination server.
You can make use of the Immediate Help that you will find in the left side menu of SWPanel to perform a test on your email account. This will check if your mail server's IP is listed in any blocking list and you will be able to see how to carry out the unblocking request.
This error usually occurs when an incorrect authentication occurs due to the user inserting the wrong credentials.
As soon as the server identifies a connection from a non-existent user, it automatically denies sending the email to its recipient by displaying the error.
You can consult the detailed configuration of your email account through SWPanel to obtain all the configuration data:
Configuration of email accounts
This message indicates that SPF, DKIM and DMARC checks have failed.
When this error is received, the email you have sent has been blocked to protect the destination user from spam and phishing.
You must verify or create the advanced SPF, DKIM and DMARC records in the DNS zone of your service using SWPanel.
To do this, you can follow the instructions provided below:
What are SPF, DKIM and DMARC records
This error indicates that the e-mail could not be delivered because it violated the policy of the receiving server.
The reason for the violation is known only to the person who configured the server. The server may have very strict rules or the content of the e-mail may contain a feature that violates these policies.
This is why you can send a blank email to check that the problem does not lie in its content.
If the behavior persists, you should contact the recipient so that they can provide you with more details on how to comply with the policy.
This error code is not very common.
It usually means that there may be a problem with the IP address of the server sending the email.
In the first instance, you should check that the DNS zone of your service has the SPF, DKIM and DMARC records necessary to pass the security check that all mail servers perform.
What are the SPF, DKIM and DMARC records
Another aspect to take into account is to check that the IP or domain name associated to your service is not marked in the blocking lists.
You can make use of the Immediate Help that you will find in the left side menu of SWPanel to perform a test on your email account to verify the previous point. If the IP or domain name is blocked, you will be able to see how to request its unblocking.
The sent email is quarantined.
The destination server usually quarantines an email when it determines that it is possibly spam.
If the email being sent is legitimate, you can either contact the recipient to accept it, or send the same message without links or attachments.
This message indicates that the destination mail server does not accept messages from the sending server because it does not have a correctly configured reverse resolution DNS record or PTR.
The reverse resolution DNS record or PTR is configured from the outgoing server, i.e. the one in charge of sending the email. A PTR record allows you to perform a reverse resolution, that is, to convert an IP to host name, as opposed to the A record of the DNS zone, which converts from domain to IP.
If you receive the returned message with this error code, you should check that the IP address assigned to your mail server has the mentioned record.
You can check how to configure the PTR record by following this manual:
The server is not able to recognize the host name (example@swmanuales.com) during DNS resolution.
You should contact the recipient informing them of the problem so that they can correct it.
This error code indicates that your sending mail server requires SMTP authentication.
This configuration must be applied in the email client / manager (Thunderbird, Outlook, etc.) of your choice used to send emails.
You can see how to configure your email account by following the manuals attached below:
Configure email accounts of my hosting in Thunderbird
Configure email accounts for my hosting in Outlook
How to set up e-mail accounts for my hosting in Microsoft Mail
This error code is very common. It refers to a type of authentication (Sender Policy Framework) that you can activate from SWPanel in your DNS zone.
To do so, you can follow the instructions provided below:
What are SPF, DKIM and DMARC records
The email account you tried to send the email to has exceeded its quota. It cannot receive the message because the mailbox is completely full.
You must contact the recipient to either extend their mailbox quota or free up space.
The error code indicates that the e-mail was rejected because it exceeded the size defined by the destination server.
The main cause is usually the attached files. You can try to compress them or split them into separate messages.
The error message indicates that the recipient's domain could not be found.
You should check that the address entered is spelled correctly, without typos, and that no spaces, periods or other punctuation marks have been entered after the recipient's e-mail address.
This error can also occur when the e-mail address you entered no longer exists or has been unsubscribed.
This message indicates that the SMTP server is configured to prevent sending mail from unauthenticated accounts.
You must check the box "My server requires authentication" or similar associated to the SMTP server of your email account (outgoing mail) in the email client / manager you use.
You can check how to configure your email account according to the client / manager you use by following the manuals attached below:
Configure email accounts of my hosting in Thunderbird
Configure email accounts for my hosting in Outlook
Configure email accounts of my hosting in Microsoft Mail
This message indicates that the SMTP server is configured to prevent sending mail from unauthenticated accounts.
You must check the box "My server requires authentication" or similar associated to the SMTP server of your email account (outgoing mail) in the email client / manager you use.
You can check how to configure your email account according to the client / manager you use by following the manuals attached below:
Configure email accounts of my hosting in Thunderbird
Configure email accounts for my hosting in Outlook
Configure email accounts of my hosting in Microsoft Mail
This error message indicates that the format of the sent email content is invalid and has been rejected.
You can compose a new email in plain format, without attachments and without the use of HTML or rich text to check that it is received correctly. If so, you should use simpler formatting in your emails to avoid rejection by the destination server.
This error usually appears when a bulk email has been sent and is marked as spam. It is usually a symptom of a compromised email account.
You can change the account login credentials using SWPanel:
How to change the password of an e-mail account
In addition, you should contact the recipient to have them mark your email account as trusted or add it to the whitelist.
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The sender's IP address is on a blacklist of addresses from which spam is sent and has been blocked by the anti-spam system of the recipient's server. The mail cannot be delivered until you resolve the situation.
To do this, you can make use of the Immediate Help that you will find in the left side menu of SWPanel to perform a test on your email account to verify the previous point. You will be able to see how to request the unblocking on the list that has marked your IP or domain name.
This message indicates that the destination mail server does not accept messages from the sending server because it does not have a correctly configured reverse resolution DNS record or PTR.
The reverse resolution DNS record or PTR is configured from the outgoing server, i.e. the one in charge of sending the email.
A PTR record allows you to perform a reverse resolution, that is, to convert an IP to host name, as opposed to the A record of the DNS zone, which converts from domain to IP.
If you receive the returned message with this error code, you should check that the IP address assigned to your mail server has the mentioned record.
You can check how to configure the PTR record by following this manual:
If you have sent an email to Hotmail, Live or Outlook, you can find the list of problems and actions to take at the following link:
If you have sent an email to Gmail, you can find the list of problems and actions to be taken at the following link: