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What is SMTP Error 550 and How to Resolve it?

What is SMTP Error 550 and How to Resolve it?

SMTP Error 550 is a common issue encountered by users when sending emails. It is a protocol-level rejection that indicates the recipient’s server has declined the message, preventing successful delivery. This error can be frustrating for both senders and recipients as it disrupts communication and requires troubleshooting to resolve.

In this article, we will explore the SMTP Error 550 in depth, providing a clear understanding of the error and offering solutions to the most frequently encountered messages associated with it.

SMTP Error 550 is a response from the recipient’s mail server that signifies a failure in email delivery. The error is part of the Simple Mail Transfer Protocol (SMTP). When an email cannot be delivered, the server sends back a 550 error code. The reasons for this error can vary, ranging from incorrect email addresses to server configuration issues.

Error 550 – Variations and Solutions

Below are ten examples of SMTP Error 550 messages, each with a brief explanation and a set of instructions on how to address the problem.

550 Requested action not taken: mailbox unavailable

Confirm the accuracy of the recipient’s email address. If correct, the issue may be temporary, such as a full mailbox, and you can attempt to resend the email later. Additionally, if possible, consider reaching out to the recipient through another channel to ensure they are aware of the issue and can take necessary action on their end.

550 5.1.1 The email account that you tried to reach does not exist

Double-check the recipient’s email address for typos. If the address is correct, contact the recipient through alternative communication to verify their email details. It’s also possible that the recipient’s email account was recently deleted or deactivated, in which case they will need to provide an alternative email address.

550 5.7.1 Unable to relay

Ensure the outgoing server (SMTP) settings in your mail client are correct, particularly if sending from a network different from your usual one.

550 5.4.5 Daily sending quota exceeded

Limit the number of emails sent within a 24-hour period or consider upgrading your email service plan to accommodate a higher sending quota. If the sending limit is a recurring issue, you may need to review your email campaign strategies or distribution lists to optimize the volume of outgoing emails. Our Email Marketing service is more suitable for sending bulk emails.

You can read SiteGround’s Acceptable Use of the Email Service Policy that explains all the limitations to service here.

550 5.2.1 Mailbox cannot receive email

The recipient or their mail provider may need to adjust mailbox settings to accept emails, or your domain may be blocked by the recipient’s email server. In some cases, the recipient’s mailbox settings may be configured to reject emails from unknown senders or those not on a pre-approved list.

550 5.7.1 Message rejected due to content restrictions

Review and modify the email content to ensure compliance with the recipient’s server policies and resend the email. Avoid using language or links that could be interpreted as spam or malicious content. It may also be helpful to ask the recipient if they have specific content filters or rules in place that could be affecting your emails.

550 5.7.1 Message rejected as spam by Content Filtering

Remove any elements that could be flagged as spam and ask the recipient to add your email address to their whitelist. Additionally, ensure that your domain has not been blacklisted by any spam monitoring services. You can find more information on why your emails may be marked as spam by the recipient’s email server in this article.

550 5.1.10 Recipient not in directory

Verify the recipient’s email address. If correct, the recipient should check their email server’s directory settings. It’s possible that the recipient’s email server requires addresses to be pre-registered before they can receive emails.

550 5.7.1 Message size exceeds fixed maximum message size

Reduce the email’s size by compressing attachments or using a file-sharing service, and consider splitting the content into multiple emails if necessary. If large attachments are a regular necessity, you may need to discuss with the recipient alternative methods of transferring files, such as using cloud storage services.

On SiteGround servers, we have set a limit of 50MB for the maximum size of an attachment in a message. This limit and other information about the email service can be found in our Email Service Acceptable Use article.

550 Message headers fail syntax check

Manually type the recipient’s email address to avoid syntax errors introduced by the mail client’s autocomplete feature. Ensure that all header fields are correctly formatted, including the ‘To:‘, ‘From:‘, ‘Subject:‘, and any custom headers that may be part of your email setup.

Error 550 FAQs

What does SMTP Error 550 indicate?

SMTP Error 550 indicates that the recipient‘s mail server has rejected the email, preventing it from being delivered. The error message accompanying the code provides details on the specific reason for the rejection, which can range from a non-existent email address to policy restrictions on the recipient’s server.

Can SMTP Error 550 be caused by a problem on the sender’s side?

Yes, SMTP Error 550 can sometimes be related to issues on the sender’s side, such as incorrect SMTP settings, sending emails that exceed the recipient server’s size limits, or sending from a domain that is not properly authenticated or is blacklisted.

Is it possible to prevent SMTP Error 550 from occurring?

While not all instances of SMTP Error 550 can be prevented, maintaining accurate email lists, adhering to email sending best practices, and ensuring your email server is properly configured can significantly reduce the likelihood of encountering this error.

What should I do if I keep getting SMTP Error 550 for a valid email address?

If you consistently receive SMTP Error 550 for an email address you believe to be valid, you should contact the recipient through alternative means to confirm the address and its status. This will help determine if the issue lies with the recipient’s email server or with the details you have on file.

How can I check if my domain has been blacklisted, which might cause SMTP Error 550?

You can use online blacklist checking tools to see if your domain has been blacklisted. If it has, you will need to follow the specific blacklist’s procedure for removal, which often involves resolving the issues that led to the blacklisting and then requesting removal from the list.

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