Yahoo Warm-up, Yahoo FBL and Yahoo bounce errors

Are you experiencing that Yahoo is blocking your emails? When sending emails to Yahoo recipients, it’s essential to follow best practices to ensure your emails are delivered successfully and don’t end up in the spam folder. Warming up your email domain and IP address can help improve your sender reputation and increase deliverability.

Here’s how to warm up when sending emails to Yahoo:

1. Start with a Small Volume: Begin by sending emails to a small number of Yahoo addresses. This allows you to gauge the initial response and ensure there are no immediate deliverability issues.

2. Gradually Increase Volume: Over time, gradually increase the volume of emails you send to Yahoo addresses. This gradual ramp-up helps Yahoo’s email servers recognize your sending patterns as legitimate and reduces the likelihood of being flagged as spam.

3. Maintain Consistency: Consistency is key to establishing a positive sender reputation. Send emails regularly to Yahoo addresses rather than sending in bursts.

4. Monitor Engagement Metrics: Keep an eye on your email engagement metrics, including open rates, click-through rates, and bounce rates. Yahoo pays attention to these metrics when determining whether to deliver your emails to the inbox or mark them as spam.

5. Authenticate Your Domain: Implement authentication protocols like SPF, DKIM, and DMARC for your domain. These protocols help Yahoo verify that your emails are legitimate and not spoofed or forged.

6. Provide Relevant Content: Ensure that your email content is relevant, valuable, and engaging to your Yahoo recipients. Irrelevant or spammy content can lead to higher complaint rates and negatively impact your sender reputation.

7. Manage Complaints: Monitor and promptly address any complaints from Yahoo users. Include a visible unsubscribe link in your emails and honor unsubscribe requests promptly to reduce the likelihood of recipients marking your emails as spam.

8. Use a Clean Email List: Regularly clean your email list to remove inactive or invalid addresses. Sending emails to inactive or invalid addresses can negatively impact your sender reputation.

9. Avoid Spam Triggers: Be mindful of spam triggers in your email content, such as excessive use of capital letters, misleading subject lines, or spammy language. Yahoo’s spam filters are sensitive to these factors.

10. Monitor Deliverability: Continuously monitor your email deliverability to Yahoo addresses using email deliverability tools or services. This allows you to identify and address any deliverability issues promptly.
Yahoo Feedback Loop:

To manage complaints, you will need to set up the Yahoo Feedback Loop (FBL) is an essential step for every email marketer.

Yahoo Feedback Loop is a service that enables users to report spam or unwanted emails sent from a particular domain or IP address.

In our documentation What is Yahoo Feedback Loop and why is it important? you can read how to set up the Yahoo Feedback Loop.

The Yahoo Feedback Loop program is designed to give email senders the ability to receive feedback on the messages they send to Yahoo email addresses.

Yahoo users who receive unsolicited messages can report the messages as spam, and this information is then passed on to the email senders. This helps senders understand why their messages are being marked as spam and take necessary actions not getting blocked by Yahoo.

Yahoo offers a Complaint Feedback Loop (CFL) program to help email senders minimize complaint rates.

Most ISP FBL’s are IP based which means that inboxroad has already signed up for those FBL’s because we manage your sending IP.

However, Yahoo is the only ISP that has a domain-based FBL. Yahoo requires two things before signing up for their feedback loop program

DKIM published on the sending domain and a postmaster@[sending domain] mailbox

Follow these simple steps to configure Yahoo FBL:

Go to the Yahoo FBL page.
Login with a Yahoo account, or create a new one.

Fill in the form (see example on the right). Make sure to fill out the following:

– Reporting Email:
– Selector: dlvm
– Request type: Add
– Domain: You should fill in the domain which you are using as your sending domain. So if you are mailing from a subdomain like, fill in If not, just fill in the root domain.

Yahoo will send a unique verification code to the postmaster@ address.
Submit this code in the form to verify.

After this, it can take up to 48 hours before they process it.

How Does Yahoo Feedback Loop Work?

Yahoo Feedback Loop is an automated system that collects feedback from Yahoo email users who report messages as spam. The FBL program sends a copy of the spam report to the email sender, which contains details of the email, such as the email address, IP address, and message content.

Email senders can use the information provided in the FBL report to identify and remove spam traps, problematic email addresses, or other issues that may affect their email deliverability. Once the sender has identified the problem, they can take the necessary steps to fix it and avoid future issues.

Benefits of Yahoo Feedback Loop

Yahoo Feedback Loop provides several benefits to email senders, including:

Improved Deliverability: Yahoo Feedback Loop helps email senders improve their email deliverability by providing feedback on why their messages are being marked as spam. This enables them to take corrective actions and avoid similar issues in the future.

Better Reputation: By receiving feedback on their email messages, email senders can maintain their reputation and avoid being marked as spammers. This helps build trust with Yahoo email users and improves their chances of getting their emails delivered to the inbox.

Reduced Spam Complaints: With Yahoo Feedback Loop, email senders can reduce the number of spam complaints they receive. By identifying and resolving issues that result in spam complaints, they can improve their email reputation and maintain a positive relationship with their subscribers.

How understand bounces errors from Yahoo?

Yahoo SMTP errors codes.

An SMTP error, or Delivery Status Notification (DSN), indicates that an email could not be delivered, either due to a temporary or permanent problem. You can review our list of SMTP error messages below for details about each error.

What are 4XX (421 and 451) temporary errors?

A 421 or 451 SMTP error indicates a temporary problem blocking the delivery of your message. Message delivery can be delayed for multiple reasons:

We’ve observed unusual traffic patterns from your sending server’s IP address.
The message you attempted to send included characteristics of spam.
Emails from your mail server have been generating complaints from Yahoo users.
The Yahoo mail servers are busy when attempting a connection.
Other suspicious behavior which leads Yahoo to enforce a dynamic deprioritization for your sender’s server.
Review Yahoo’s Sender Requirements & Recommendations to learn how you can help your emails reach Yahoo.
If you encounter 4XX errors when trying to send an email to Yahoo, you may retry sending at a later time.

What are 5XX (553 and 554) permanent errors?

A 553 or 554 SMTP error indicates an email could not be delivered due to a permanent problem. Message delivery can be permanently deferred because:
You’re trying to send a message to an invalid email address.
Your message failed authentication checks against your sending domain’s DMARC or DKIM policy.
The message contains characteristics that Yahoo won’t accept for policy reasons.
Other suspicious behavior which leads Yahoo to issue a permanent rejection for your SMTP connection.
Your IP is listed by Spamhaus. Please check with
If you consistently receive 5xx errors when sending to Yahoo, we encourage you to review our Sender Requirements & Recommendations, since 5xx errors can be a symptom of a more widespread, general problem.
You should not retry sending an email that comes back with with a 5xx error. List managers should have a policy for removing email addresses that generate 5xx errors/bounces.

Content based blocks (e.g: PH* Errors)

These error messages indicates that your email wasn’t accepted because there is something in the content that Yahoo won’t accept for policy reasons.
Objectionable content that Yahoo deems unacceptable includes:
– Viruses
– Phishing attempts
– Ransomware
– Other malicious software
– Links or URLs to any of the above

Examine your outbound queues for potentially objectionable content to ensure that spammers aren’t abusing your mail server.
Follow our Sender Requirements & Recommendations and make appropriate changes to secure your servers

A key mission of Yahoo is to deliver messages that consumers want to receive and filter out the messages they don’t. The best way to ensure your messages are delivered is to send timely and relevant email to an active and engaged audience.

If having any other questions don’t hesitate to contact us at or Daniel our email deliverability expert at