Yahoo! troubleshooting support information

Starting February 1, 2018, Verizon Media (a Verizon company that owns both AOL and Yahoo!) began consolidating sending infrastructures between AOL and Yahoo!. This means that the AOL domains will continue to operate and accept email, but Yahoo! will handle spam filtering and processing.

You can get additional information about the changes and the impact here:

If you send email to AOL domains, we recommend that you follow best practices for both AOL and Yahoo! during this transition period.

Yahoo! troubleshooting resources

Prior to submitting a support request to Yahoo!, be sure you are following their best practices and try to fix the cause of your deliverability problems.

Basic steps to troubleshoot bulking at Yahoo!

Here are some troubleshooting steps you should take if you are experiencing bulking at Yahoo!

  • Are you signed up to the Yahoo! FBL and actively processing or removing those who complain? If you are not signed up you can do so on the Yahoo Postmaster website.
  • Are you sending to subscribers that are engaged with your email? Sending to subscribers that have engaged with your email (open and/or clicked) within a set period of time can help reduce bulking. Analyze your subscribers’ engagement over the past 12 months and if you are still experiencing bulking try limiting your sending to an engagement window of 9 months to see if that resolves the bulking issue.
  • Are you sending too frequently? If you are sending multiple times a week you may want to try reducing that to see if there is any benefit to your complaint rate.
  • Do you have an unsubscribe link at the top of your email? Some senders see a benefit by adding another unsubscribe link to the top of the email, this makes it easier for a subscriber to unsubscribe instead of mark the email as spam (TIS).

Bulking at different Yahoo! domains

If you are experiencing bulking at a Yahoo! regional domain (for example, or a partner domain such as but are achieving nearly 100% inbox placement at, you might assume that there is something wrong with the CoreSeeds or SmartSeeds or that something is broken at Yahoo!. This is not the case. 

Delivery across Yahoo! domains can be inconsistent even when content and mailing practices are consistent across all domains. This is due to list issues such as list age, engagement, complaints, and the overall quality of the list at the domain in question. Although Yahoo! has never explicitly confirmed it, Return Path believes that Yahoo! processes the domains separately. The same filters are applied on all domains, but the lists on each domain will impact reputation on that domain. This impacts inbox delivery. 

To determine why email to one domain is bulking, you should review your list at that domain. You should also compare your data for to the domain in question, specifically:

  • List management (are mailing practices the same at both domains?)
  • Complaints (raw complaints and complaint percentage)
  • Average age of list
  • Opens, clicks, unsubscribes, complaints, and churn

Senders should:

  • Review and update the list-unsubscribe or re-confirm subscribers who have not engaged at all recently (six months is usually a good start)
  • Adjust frequency, especially to less-engaged subscribers

Sending to engaged subscribers and less frequent mailing to less engaged subscribers boosts reputation. Inbox delivery should recover within a few weeks. 

Blocked mail

It is important to determine if email is definitely being blocked prior to contacting Yahoo! to request block removal. This can only be done with certainty by reviewing error codes in your SMTP mail logs, which you’ll either need to do internally if you host your own email server, or have your email service provider do for you. 

Following are examples of a variety of error codes indicating blocks, deferrals (also referred to as throttling) and hard bounces due to unknown users. 

Error codes 

Blocks or hard bounce errors:

  • 554 Message not accepted for policy reasons: This is most often a reputation issue. It could be content as well, but reputation is the first cause.
  • 554 5.7.5 (AU01) Message not accepted for policy reasons when sending to Yahoo!. This error message indicates that your email wasn't accepted because it failed authentication checks against your sending domain's DomainKeys or DKIM policy.
  • 554 delivery error: This user does not have a account (<redacted> The email didn't go through because the recipient's user ID doesn't exist. You shouldn't retry the message, and remove the email address from your list. It will never complete successfully.
  • 550 5.7.1 [BLXX] Connections not accepted from IP address on Spamhaus when sending email to Yahoo! IP is listed on Spamhaus, you will need to contact them directly.
  • PH01 (phishing) and MW01 (malware): The sender was probably compromised or hacked. It is likely that a URL was marked as phishing, maybe from PhishTank, or through other external or internal lists. If the block does not lift on its own after the compromise is fixed, request Return Path mediation. To remediate a PH01 error:
  • Isolate the URL that is causing the error.
  • Open a ticket to Yahoo! Customer care and provide the URL for further investigation.
  • 550 5.7.1 Unauthenticated email is not accepted from this domain: This error indicates that the email is blocked for Domain-based Message Authentication, Reporting, and Conformance (DMARC) failures. 

Getting a block removed

After you have determined that your email is in fact being blocked, and the reason if it is provided in the error code, you should gather as much data as possible in the Return Path tools as well as response data. This will help you determine if you have a sending issue, such as a sharp volume increase, a large increase in complaints or spam traps, or a drop in opens or clicks. Any of these issues could indicate a problem with the email or your list. You may have to take steps to correct the issue, such as reducing your complaint rate, before you request that Yahoo! Remove the block.

You can submit a block removal request and Yahoo usually responds within a couple of days. Please be advised that Yahoo! does not review CoreSeed or SmartSeed issues for any domain or partner domain. If you have questions about CoreSeeds or SmartSeeds, you should contact Return Path Support or your Account Manager. 

Temporary bounces or deferrals:

  • 421 Message from (x.x.x.x) temporarily deferred - [numeric code]. The message  the sender attempted to send exhibited characteristics indicative of spam. It indicates that emails from the mail server have been generating substantial complaints from Yahoo! Mail users. It is a temporary error and the mail server may automatically retry sending emails at a later time.
  • 451 Message Temporarily deferred: Errors such as 451 Message temporarily deferred - 140 seem to be transient.

421 TS01, TS02, and TS03: For senders with insufficient reputation or sending history, deferrals are common. These diagnostic codes may allude to an issue with complaints:

 TS01: This error indicates Yahoo! is seeing unusual traffic from a sender's IP address or that emails from the sender's mail server are generating complaints from Yahoo! Mail users. The error is temporary. However, senders will continue to receive the error message as long as they receive complaints. Senders must resolve the complaint.

TS02: TS01 errors can turn into TS02 errors if not addressed. Senders with TS02 errors should take immediate action to address complaints. These errors place senders closer to a permanent error at Yahoo! Once a permanent error occurs, the IP address will be blocked and mail will not be delivered to the end user. Lessen the volume until the error has stopped, then ramp the volume back up again.

TS03: A TS03 error indicates a permanently deferred state. Messages receiving TS03 will not be delivered upon retry. This error message indicates Yahoo! is seeing a high volume of messages from the sender's IP address that is characteristic of unsolicited bulk emails. While this is a temporary SMTP error code, Return Path does not recommend attempting to resend the messages until the sender examines subscription practices and lists and implements changes to ensure that messages are sent only to subscribers who have requested them. Resolve the issue by addressing complaints and lowering volume.

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