How Yahoo Mail answers a verification check
Yahoo and AOL addresses share Yahoo's mail infrastructure under yahoodns.net. When an account does not exist, Yahoo answers in plain words, for example "554 delivery error: dd This user doesn't have a yahoo.com account".
Yahoo is quick to defer senders it does not know well. Its deferrals carry bracketed TS codes such as [TS01] or [TSS04], which Yahoo documents as temporary deferrals caused by complaints, spam-like content, IP reputation or unusual traffic. None of these say anything about the mailbox. Yahoo's own error reference also tells senders with excessive unknown recipients to remove any addresses that generate bounces.
Yahoo Mail replies and what RocketVerifier returns
Each SMTP reply maps to one status and sub-status. Replies about the probing server are never counted against the address.
| Reply | Result | What it means |
|---|---|---|
| 250 recipient <name@yahoo.com> ok | deliverable none | The account exists. |
| 554 delivery error: dd This user doesn't have a yahoo.com account | undeliverable mailbox_not_found | No such account. Remove it. |
| 421 4.7.0 [TSS04] Messages from x.x.x.x temporarily deferred | unknown blocked | A sender deferral. Not charged. |
| 554 5.7.9 Message not accepted for policy reasons | unknown blocked | A permanent policy rejection of the sender or message, not the mailbox. |
What RocketVerifier does differently for Yahoo Mail
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Yahoo's bracketed codes decoded
Any [TS..], [TSS..] or [BL..] code is read as a block on the sender, and the "doesn't have a yahoo.com account" wording as a definite missing mailbox.
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The slowest, most careful pacing
Yahoo gets the gentlest session profile in the engine: the longest pause between commands and a few recipients per session, inside its own per-IP budget.
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Warmed IPs only
New verification IPs do not query Yahoo until they are past the early warm-up stages.
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A block is never a bad address
Replies about the probing IP, rate or policy are returned as unknown with the blocked sub-status and never charged. Only an explicit mailbox answer becomes deliverable or undeliverable.
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Deferrals retried for you
Temporary deferrals are retried automatically, up to three times about ten minutes apart, before a final result is returned.
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No email is ever sent
The SMTP conversation stops at RCPT TO, before DATA. Your recipients never see a probe.
Sending to Yahoo Mail: what to get right
- Yahoo requires all senders to use SPF or DKIM, valid forward and reverse DNS and a spam rate below 0.3%. Bulk senders also need SPF and DKIM, a DMARC policy of at least p=none, one-click unsubscribe and unsubscribes honoured within 2 days.
- AOL addresses are Yahoo addresses for deliverability: same servers, same rules.
- If Yahoo defers your campaigns with a TS code, cut volume, remove unengaged addresses and verify the list before ramping back up. Yahoo flags excessive unknown recipients on its own.
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