Yahoo and AOL troubleshooting
Yahoo and AOL SMTP errors, explained
Understand Yahoo and AOL delivery errors, temporary deferrals, policy rejections, mailbox failures and RFC header problems.
Search by Yahoo’s provider tag or stable response wording as well as the numeric SMTP code.
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Yahoo 421 4.7.0: Yahoo temporary policy deferralYahoo 421 4.7.0: Yahoo temporary policy deferral. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 451 4.3.0: Yahoo temporary mail system failureYahoo 451 4.3.0: Yahoo temporary mail system failure. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 451 4.7.0: Yahoo resources temporarily unavailableYahoo 451 4.7.0: Yahoo resources temporarily unavailable. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 552 5.2.2: Yahoo mailbox quota exceededYahoo 552 5.2.2: Yahoo mailbox quota exceeded. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 553 5.1.1: Yahoo user not foundYahoo 553 5.1.1: Yahoo user not found. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 553 5.2.2: Yahoo mailbox fullYahoo 553 5.2.2: Yahoo mailbox full. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 554 5.6.0: Yahoo RFC header rejectionYahoo 554 5.6.0: Yahoo RFC header rejection. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 554 5.7.1: Yahoo message not allowedYahoo 554 5.7.1: Yahoo message not allowed. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 554 5.7.1: Yahoo PH01 policy rejectionYahoo 554 5.7.1: Yahoo PH01 policy rejection. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo 554 5.7.1: Yahoo PH02 policy rejectionYahoo 554 5.7.1: Yahoo PH02 policy rejection. Understand the response, identify ownership, and follow an evidence-based next step.
Yahoo TSS04: Messages temporarily deferredYahoo 421 4.7.0 TSS04 temporarily defers a sending IP after unexpected volume or user complaints; slow down, preserve retries, and correct the traffic signal.
Yahoo TSS06: All messages permanently deferredYahoo 553 5.7.2 TSS06 permanently defers mail from the cited IP; stop retries, remediate the sender and request Yahoo review.
Yahoo 553: Mail From address not allowedYahoo 553 Mail From not allowed is a permanent rejection of the SMTP envelope sender; use the complete response to correct its address, domain, authorization, or policy problem.
Yahoo TS01: Messages temporarily deferredYahoo TS01 is a temporary sender deferral; slow Yahoo and AOL traffic, preserve retries, and use the complete response to correct volume, complaints, content, or reputation.
Yahoo TS03: All messages temporarily deferredYahoo TS03 means all mail from the cited source is temporarily deferred; pause expansion, preserve backoff, and remediate the sender stream before escalation.
Yahoo TSS07: Sending IP listed by SpamhausYahoo 553 5.7.1 TSS07 rejects a connecting IP listed by Spamhaus; stop retries, identify the IP owner, remediate the source, and follow the listing process.
Yahoo 554 Message not allowedResolve Yahoo 554 Message not allowed by using the full response to distinguish authentication, content, reputation, and sender-policy causes.
Yahoo 554: Headers are not RFC compliantFix Yahoo RFC compliance failures caused by duplicate or malformed headers, incorrect MIME types, and broken message generation.
Yahoo 554: This user does not have a Yahoo.com accountResolve Yahoo user does not exist bounces by verifying the recipient and removing permanently invalid addresses from mailing lists.
Yahoo: Message temporarily deferred (TS* errors)Resolve Yahoo Message temporarily deferred and TS* errors by slowing retries and finding the affected traffic or reputation signal.
Primary sources: Yahoo Sender Hub SMTP errors.