Yahoo and AOL Bounce Codes: What Each Error Means and What to Do
Yahoo bounces fall into two classes: 4xx codes (421, 451) are temporary and retry on their own, and 5xx codes (553, 554) are permanent and must not be retried. The one you can fix with your list is 554 delivery error: dd This user doesn't have a yahoo.com account, which means the mailbox doesn't exist: remove it. TS codes such as TSS04 are temporary deferrals about your volume or reputation, PH codes are content blocks, and the rest are complaint, authentication or policy errors about your sending. AOL uses the same system.
Check a Yahoo or AOL address before you send:
Step 1: know what Yahoo does and doesn't publish
Gmail and Microsoft publish code-by-code tables. Yahoo doesn't. Its SMTP error codes page on the Sender Hub (read 8 November 2026) describes categories and gives one full sample line. So read the whole text your server logged, not just the number.
The page applies to every Yahoo-hosted domain: yahoo.com and its country versions, ymail.com, rocketmail.com, aol.com and ISP addresses Yahoo hosts. Our list of Yahoo email domains has the full set, with the MX records we checked.
Step 2: match the bounce to its category
| Yahoo's category | What you see | What Yahoo says to do |
|---|---|---|
| Recipient does not exist | 554 delivery error: dd This user doesn't have a yahoo.com account |
Don't retry; "remove the email address from your mailing list" |
| Excessive unknown recipients | Many of the above in one send | "Review your mailing lists and remove any addresses that generate bounces" |
| Message temporarily deferred (TS* errors) | 421 4.7.0 [TSS04] ... temporarily deferred and similar |
Retry later; check your outbound queue for abuse; file a Sender Support Request if it persists |
| Content based blocks (PH* errors) | A rejection with a PH code | Follow Yahoo's sender requirements and secure your servers |
| Excessive user complaints | Deferrals or blocks tied to complaints | Monitor your sender reputation |
| Excessive unsolicited messages | A block naming unsolicited mail | Don't resend until you've reviewed Yahoo's sender requirements |
| Authentication failures | A rejection naming SPF or DKIM | "All senders need to authenticate their emails with either SPF or DKIM" |
| Unresolvable RFC 5321 or 5322 from domain | 451 (timeout) or 554 (permanent) |
Make sure your From and Return-Path domains resolve, including an SOA record |
| RFC compliance failures | A rejection naming RFC compliance | Fix the message headers |
| Resources temporarily unavailable | A temporary error on Yahoo's side | Usually brief; let your server retry |
| Other policy errors | 550 or 554 |
Yahoo "may permanently defer or reject mail for policy reasons" |
The recipient bounce in detail
Yahoo's sample failure line is:
554 delivery error: dd This user doesn't have a yahoo.com account ([email protected]) [-5] - mta123.mail.mud.yahoo.com
Two things trip up bounce handling. The reply is 554, not 550, and there's no enhanced code like 5.1.1. A rule that only suppresses 550 or 5.1.1 lets this address stay on your list and bounce again next week. Match on any 5xx plus "doesn't have a" or your platform's own hard-bounce flag. The one-line version is on our Yahoo 554 code page.
Deferrals (TS codes)
421 4.7.0 [TSS04] is the most common. Yahoo says it's temporary and lists causes such as complaints from Yahoo users, spam-like content, poor IP reputation and unusual traffic. Pushing more mail through makes it last longer. Our TSS04 guide has the step-by-step fix.
Unknown recipients as a reputation problem
Yahoo treats a high share of unknown recipients as a signal about the sender, separate from each bounce. One old list can slow delivery to every Yahoo and AOL address you mail afterwards. See Yahoo excessive unknown recipients.
Step 3: sort a batch of Yahoo bounces
- Split 4xx from 5xx. Leave 421 and 451 to your server's retries; if they last, send less to Yahoo domains.
- Pull out authentication and from-domain errors. Fix SPF, DKIM and DMARC first. The Gmail and Yahoo bulk sender requirements post lists what Yahoo expects from bulk senders.
- Pull out complaint, unsolicited and PH errors. Review where the list came from and what you sent.
- Suppress every "doesn't have a yahoo.com account" address in your sending tool and in the source file.
- If errors continue after you've fixed what you can see, file a Yahoo Sender Support Request with the exact lines from your logs.
Paste a bounce into the bounce message analyzer if you can't tell which category it is.
Prevent the recipient bounces
- Check the list before you send. Upload it on the verify page: every address gets a live mailbox check, and valid, risky and invalid download as separate files.
- Yahoo addresses are harder to confirm than Gmail ones, for reasons covered in why Yahoo addresses are hard to verify. Expect some to come back risky (unconfirmed); send those in a smaller batch to Yahoo first.
- Have a file that's mostly Yahoo and AOL? The bulk Yahoo email checker and bulk AOL email checker are built for it.
Before an old-list send, our page on checking if an email address exists explains what a mailbox check can and can't tell you.
Where SimpleVerifier fits
The first 100 checks are free with a Google sign-in, no card. Starter is $9 a month for 2,500 checks; Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off. See pricing.
Common questions
What does 554 delivery error: dd This user doesn't have a yahoo.com account mean?
The Yahoo account you sent to doesn't exist. Yahoo's Sender Hub says you should not retry, the message 'will never complete successfully', and you should remove the address from your list.
What does 421 4.7.0 [TSS04] mean from Yahoo?
A temporary deferral. Yahoo lists possible causes as complaints from its users, content that looks like spam, poor IP reputation and unusual traffic. Your server retries; slow down and fix the cause, and file a Sender Support Request if it persists.
Does Yahoo use enhanced status codes like 5.1.1?
Not consistently. Its documented missing-user sample has a 554 reply and no enhanced code, so a bounce parser that only looks for 550 or 5.1.1 misses it. Match on the 5xx class plus the text.
Do Yahoo bounce codes apply to AOL?
Yes. AOL Mail runs on Yahoo's mail infrastructure, and Yahoo's Sender Hub covers both, so AOL bounces use the same categories and codes.
Can email verification prevent Yahoo bounces?
It removes the dead addresses that cause 'doesn't have a yahoo.com account' bounces and the unknown-recipient reputation hit. Yahoo addresses are harder to confirm than Gmail ones, so expect some to come back risky. Deferrals, complaints and authentication errors come from your sending, not the list.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.