SMTP Yahoo Error Codes Explained
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If Yahoo mail delivery issues have been bugging you recently, this article is for you! Yahoo has started blocking unauthenticated messages that don’t meet their latest guidelines. When your Yahoo email fails to get delivered, Yahoo may send you an error code. It is crucial to understand what these Yahoo error codes mean, to troubleshoot the error quickly.
Yahoo Emails Bouncing Back with 550 Error Code
As of May 1st 2024, Yahoo emails have officially started bouncing back for several senders with the following Yahoo error message:
550 5.7.9 This mail has been blocked because the sender is unauthenticated. Yahoo requires all senders to authenticate with either SPF or DKIM.
This Yahoo error message can be broken down to analyze why the sender was unsuccessful at sending their message to a Yahoo inbox:
- The email was unauthenticated
- The sender lacked SPF and DKIM records in their DNS
- Either of these records are required by Yahoo for authentication
- Hence, Yahoo blocked the email from being delivered
General email senders who haven’t yet configured mandatory email authentication protocols like SPF or DKIM and bulk senders who are yet to enable DMARC for their domains will continue to face email deliverability issues with Yahoo. To deliver your emails successfully, compliance with the latest Yahoo requirements is a must!
PowerDMARC’s Google and Yahoo compliance program is the easiest way to make your emails compliant at the fastest market speed. Following your onboarding, our experts will guide you through your SPF, DKIM, and DMARC setups. Once done, all your legitimate messages will land in your client’s inboxes – without any issues!
What is a Yahoo SMTP Error Code?
An SMTP error code is a numerical response code sent to indicate the outcome of an email sent through SMTP (Simple Mail Transfer Protocol). SMTP generates codes to communicate the status of mail delivery (success or failure). The error code is usually accompanied by a message that describes the error. This message is usually short, and it explains why the email was rejected or the issue encountered during the transfer.
For example, Yahoo error code 421 can describe a temporary error due to service blockages. Yahoo error code 554 depicts a permanent error due to authentication failures.
Common Yahoo Error Codes Debunked
| Error Code | Type | Description |
| 421 / 451 | Temporary | Temporary block due to spam, complaints, connection issues, or service unavailability delaying email delivery. |
| 550/553 / 554 | Permanent | Permanent rejection due to non-compliance, authentication failure, or blocklisting. |
Yahoo mail delivery errors can be grouped into 2 categories: temporary errors and permanent errors. In this article, we will be touching base on temporary errors while explaining permanent error codes in detail.
1. 4XX (421 and 451) Temporary Error Code
4XX Error Description
Your Yahoo email can be temporarily blocked due to a temporary error. Yahoo error codes 421 and 451 might be sent to you in such a situation. Temporary errors, while won’t lead to outright rejections, can postpone the delivery of your email.
Reasons for 4XX Temporary Errors
You can receive the 4XX (421 and 451) Yahoo temporary error codes if:
- You keep sending bulk messages from a particular IP, which can potentially spam Yahoo inboxes
- Yahoo has received complaints against your email sending practices from receivers
- Connection failures, outages, or temporary service unavailability
How to Fix Yahoo 421 and 451 Errors?
To fix Yahoo’s temporary errors, you can:
- Enable one-click unsubscribe for your email messages
- Make sure you are sending messages that interest your receivers
- Not indulge in any suspicious activities
- Follow RFC-compliant message formatting
- Try sending the email again after some time
2. 5XX (550, 553 and 554) Permanent Error Code
5XX Error Description
Unlike temporary errors, which may auto-resolve, the 5XX permanent errors may lead to permanent message rejections. Yahoo sends 553 and 554 error codes to depict permanent errors in message delivery. If you come across these error codes, you must take action now!
Reasons for 5XX Permanent Errors
You can receive the Yahoo 550, 553 and 554 error messages if you:
- Fail to comply with Yahoo’s bulk sender guidelines
- Your message failed email authentication checks for DMARC, SPF, or DKIM
- Your bulk messages are unauthenticated (i.e. missing DMARC, SPF and/or DKIM setup)
- Yahoo suspects illegal or suspicious activities originating from your domain
- Your domain is blocklisted on a popular DNS blocklist like Spamhaus
There are several other reasons that may trigger the Yahoo 554 error code. The reason can be as simple as sending an email to an address that doesn’t exist! The reason can also be as complex as DMARC failure.
Whatever may be the reason, to prevent email deliverability issues, you must fix it promptly!
How to Fix Yahoo 550, 553 and 554 Errors?
If you notice Yahoo 550, 553 and 554 error codes for your message, you can fix them by following these steps:
- Setup SPF, DKIM, and DMARC for your domain
- Monitor your authentication status and deliverability using DMARC reports
- Make sure your messages are of value to Yahoo receivers
- Make your promotional messages easy to unsubscribe
- Maintain a low spam rate for your emails and avoid getting blocklisted
Yahoo warns against resending emails that encounter permanent errors like 553 and 554.
You can check out Yahoo’s document here to view the complete list of Yahoo error codes.
Fixing “550 5.7.9 Sender is Unauthenticated” Yahoo Error
To fix the 550 5.7.9 Sender is Unauthenticated Yahoo Error you need to set up email authentication for your sending domain. This includes configuring SPF, DKIM, and DMARC records. You can follow the steps given below to get started:
1. Create and publish an SPF record (all senders)
Sign up for free on PowerDMARC and use our SPF record generator tool to create your SPF record. Authorize your sending sources and configure a failure mechanism (i.e. ~all for Softfail). Once generated, publish this SPF record on your DNS with the help of your domain registrar.
2. Or, create and publish a DKIM record (all senders)
While you can configure either SPF or DKIM to gain compliance with Yahoo, we recommend both for enhanced security. You can select our DKIM generator tool to create your free record. Once generated, publish this record on your DNS with the help of your domain registrar.
3. Enable DMARC for your domain (bulk senders only)
Those sending more than 5000 emails a day, need to additionally implement DMARC. When you create your DMARC record using our DMARC record generator tool, make sure you configure the following mandatory fields:
- v=DMARC1 (protocol version)
- p=(the policy of your choice between reject, quarantine and none)
Once generated, publish this record on your DNS with the help of your domain registrar.
Note: We recommend all email senders set up DMARC in addition to SPF and DKIM (not just bulk senders). This is because DMARC helps prevent spoofing, phishing, and impersonation attacks. However, DMARC implementation at an enforced policy (reject/quarantine) must be exercised with caution and followed up with monitoring efforts. This will ensure your legitimate emails don’t get blocked.
For expert assistance, contact us today!
Fixing “554 5.7.9 Message Not Accepted for Policy Reasons” Yahoo Error
A permanent Yahoo error message senders frequently face post the Yahoo sender policy updates is the “554 5.7.9 Message Not Accepted for Policy Reasons” error. This may be triggered if your domain lacks (or fails) DMARC authentication.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol. DMARC can help you authenticate your domain name, monitor email delivery, and prevent phishing attacks. Yahoo has asked email senders sending more than 5000 emails per day to configure DMARC for their domains.
Note: Yahoo’s 554 troubleshooting guide explains that your email may be rejected if you are on p=reject while failing DMARC authentication. You can learn more about failure reasons and prevention in our DMARC fail guide.
5 Steps to Fix 554 5.7.9 Yahoo Error
Before proceeding to troubleshoot the error, check if your domain is already DMARC compliant. Use our free domain checker tool.
1. Configure SPF or DKIM
To implement DMARC, you need to have either SPF or DKIM enabled for your domain. Sign up with us for free to set up these protocols in a few minutes!
2. Create a DNS Record for DMARC
Create your DMARC record using our DMARC generator tool.
3. Select a DMARC Policy
While Yahoo supports a minimum DMARC policy of “none”, our experts don’t recommend it. Domain owners should start with a “none” policy with the long-term goal of shifting to “reject”.
4. Upload DMARC Record to DNS
Access your DNS management console to publish your DMARC record. If you don’t have access, contact your domain administrator at once!
5. Monitor Your Email Deliverability
After you have successfully implemented DMARC, it is important to enable DMARC reports. These reports will help you monitor Yahoo mail delivery issues.
Resolve Yahoo Mail Delivery Issues with PowerDMARC
PowerDMARC’s Google and Yahoo Compliance Program has been actively helping businesses around the world meet sender guidelines. If you are struggling with SPF, DKIM, and DMARC implementation – we have got you covered! Our hosted solutions and seasoned experts help you deploy the protocols easily! We also make your DMARC reports easy to read, so you can detect issues quickly.
Thousands of organizations have achieved DMARC compliance with PowerDMARC, and so can you. Get started today!
Domain & Email Security Expert at PowerDMARC
Yunes is an Operations Team Lead at PowerDMARC with expert knowledge in email authentication and security. Yunes is a Microsoft-certified Azure Administrator Associate with certifications in CompTIA A+ and many more.
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