Typical mistakes you can make when sending an email
When sending an email, you may occasionally find that it has been returned to your mailbox without reaching the recipient, indicating an error. Below, we explain what the most common error messages you may receive mean:
All error codes starting with 550 indicate that your email has been returned by the destination server.
It is important to highlight that more detailed information is provided in the body of the message, so it will always be useful to read its content in full.
Error 550 5.1.0 Address Rejected
This error indicates that the destination server does not accept your email. Although the message itself does not provide more information, the main reason is usually a block.
As far as possible, you should contact the recipient so they can unblock your email account or domain, or so that their provider can provide them with more details.
Error 550 5.1.1
The error indicates that the email account or the domain entered as the recipient does not exist.
You should check that the address you have indicated does not have typographical errors, spaces between characters, or incorrect punctuation marks.
Error 550 5.2.1
With this error, we can encounter 2 different scenarios:
- The email account you tried to send your message to is disabled.
- The recipient of your email is receiving a large amount of mail which prevents more messages from being delivered.
In both cases, you must contact the recipient so they can correct this behavior.
Error 550 5.4.1
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 propagation process of the same.
You can check the DNS configuration of your service by following this link:
Error 550 5.7.0 Message Size Violation
The error code indicates that the sending of the email has been rejected for exceeding the size defined by the destination server.
The main cause is usually the attached files. You can try to compress them or divide them into different messages.
Error 550 5.7.1 Rejected
The error code indicates that the email has been rejected due to a problem or a security policy on the destination server.
You can use the Immediate Help found in the left side menu of SWPanel to perform a test on your email account. In this way, it will be verified if the IP of your mail server is listed on any blocklist and you will be able to see how to carry out the unblocking request.
Error 550 5.7.1 Authentication Required
This error usually occurs when an incorrect authentication takes place due to the insertion of erroneous credentials by the user.
The moment the server identifies a connection from a non-existent user, it automatically denies the sending of the email to its recipient, displaying the error.
You can consult the detailed configuration of your email account through SWPanel to obtain all the configuration data:
Error 550 5.7.26 Authentication Required
This message indicates that the SPF, DKIM, and DMARC checks have not been passed.
When this error is received, the email you sent has been blocked to protect the destination user against spam and phishing (identity theft).
You must verify or create the advanced SPF, DKIM, and DMARC records in the DNS zone of your service through SWPanel.
To do this, you can follow the instructions provided below:
Error 550 Denied By Policy
This error indicates that the email could not be delivered because it violated the policy of the server receiving it.
The reason for the violation is only known by the person who configured the server. It may be that it has very strict rules or that the content of the email contains some characteristic that violates these policies.
That 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 they can provide you with more details to comply with the established policy.
Error 550 Administrative Prohibition
This error code is not very common.
It usually refers to the fact that there may be a problem with the IP address of the server sending the email.
First, you should check that the DNS zone of your service has the necessary SPF, DKIM, and DMARC records to pass the security verification that all mail servers perform.
Another aspect to keep in mind is to check that the IP or domain name associated with your service are not marked in the blocklists.
You can use the Immediate Help found 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 found to be blocked, you will be able to see how to request its unblocking.
Error 550 Quarantined
The sent email is in quarantine.
The destination server usually puts an email in quarantine when it determines that it might be spam.
If the email being sent is legitimate, you can contact the recipient so they can accept it, or send the same message without links or attachments.
Error 550 Reverse DNS
This message indicates that the destination mail server does not accept messages from the sending server, as it does not have a reverse DNS resolution or PTR record configured correctly.
The reverse DNS resolution or PTR record is configured from the outgoing server, that is, the one responsible for sending the email. A PTR record allows a reverse resolution to be performed, that is, converting an IP to a hostname, opposite 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 must check that the IP address assigned to your mail server has the aforementioned record.
You can check how to configure the PTR record by following this manual:
Error 550 Host Unknown
The server is unable to recognize the hostname (example@swmanuales.com) during DNS resolution.
You should contact the recipient informing them of the problem so they can correct it.
Error 550 Authentication is Required for Relay
This error code indicates that your mail server in charge of sending requires SMTP authentication.
This configuration should be applied in the email client / manager (Thunderbird, Outlook, etc.) of your preference used to send emails.
You can see how to configure your email account by following the manuals attached below:
Error 550 SPF
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 this, you can follow the instructions provided below:
Error 552 5.2.2 Over Quota
The email account you tried to send the email to has exceeded its established quota. It cannot receive the message since the mailbox is completely full.
You must contact the recipient so they can increase their mailbox quota, or release space.
Error 552 5.2.3
The error code indicates that the sending of the email has been rejected for exceeding the size defined by the destination server.
The main cause is usually the attached files. You can try to compress them or divide them into different messages.
Error 553 5.1.2 Recipient Address not Valid
The error message indicates that the recipient's domain could not be found.
You should check that the address entered is written correctly, without typographical errors, and that no spaces, dots or other punctuation marks have been entered after the recipient's email address.
This error can also occur when the email address you have indicated no longer exists or has been deactivated.
Error 553 "Sorry, that domain isn't allowed to be relayed thru this MTA (#5.7.1)"
This message indicates that the SMTP server is configured to prevent sending mail from unauthenticated accounts.
You must check the "My server requires authentication" box or similar associated with the SMTP server of your email account (outgoing mail) in the mail 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:
Error 553 "Sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)"
This message indicates that the SMTP server is configured to prevent sending mail from unauthenticated accounts.
You must check the "My server requires authentication" box or similar associated with the SMTP server of your email account (outgoing mail) in the mail 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:
Error 554 5.6.0
This error message indicates that the format of the content of the sent email is not valid and has been rejected.
You can write a new email in plain text 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 formats in your emails to avoid their rejection by the destination server.
Error 554 5.7.0
This error usually appears when a mass sending of email has been carried out and is marked as spam. Normally, it is a symptom of a compromised email account.
You can change the access credentials to the account through SWPanel:
Additionally, you should contact the recipient so they can mark your email account as trusted or add it to the whitelist.
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Error 554 "The IP address of the sender was found in a DNS blacklist database and was therefore refused."
The sender's IP address appears on a blacklist of addresses from which spam is sent and has been blocked by the antispam system of the recipient's server. The email cannot be delivered until the situation is resolved.
To do this, you can use the Immediate Help found 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 from the list that has marked your IP or domain name.
Error 554 "This server requires PTR for unauthenticated connections"
This message indicates that the destination mail server does not accept messages from the sending server, as it does not have a reverse DNS resolution or PTR record configured correctly.
The reverse DNS resolution or PTR record is configured from the outgoing server, that is, the one responsible for sending the email.
A PTR record allows a reverse resolution to be performed, that is, converting an IP to a hostname, opposite 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 must check that the IP address assigned to your mail server has the aforementioned record.
You can check how to configure the PTR record by following this manual:
General Hotmail Errors
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:
General Gmail Errors
If you have sent an email to Gmail, you can find the list of problems and actions to take at the following link: