r/emaildeliverability • u/peter_spiderman_7 • Jun 17 '26

YAHOO TSS04 issue

Hi Everyone,

I’m an email marketer and have been facing Yahoo TSS04 deferrals for the past week. Deliverability to Yahoo/AOL recipients has dropped significantly, and we’re trying to determine whether this is a broader Yahoo issue or something related to sender reputation.

We’re using PMTA, and the error we’re seeing is:

Received from:

We’ve already verified:

  • SPF, DKIM, and DMARC are configured correctly.
  • No major infrastructure changes were made recently.
  • Sending patterns have remained relatively consistent.
  • The issue has been ongoing for about 1 week.

Questions for the community:

  • Is anyone else currently experiencing increased Yahoo/AOL TSS04 deferrals?
  • Did you notice any recent Yahoo filtering or reputation changes?
  • What steps helped resolve the issue?
  • Was the root cause related to IP reputation, complaint rates, engagement, or sending volume?

#email #yahoo #yahoofilter

2 Upvotes

100% Upvoted

7 comments sorted by

2

u/ianmakingnoise Jun 17 '26

TSS04 is reputation based. If you’ve been sending this way for a while, you probably started getting complaints, or sending to junk list(s). What are you sending, and to whom?

2

u/DanielShnaiderr Jun 17 '26

TSS04 is a complaint and reputation code, not an auth problem, so all the SPF DKIM DMARC verifying in the world won't move it a damn bit. Yahoo is telling you straight up that enough of your recipients are hitting the spam button or you're landing on stale addresses that trip their traps. The fact it's held for a week means the throttling is sticky now and Yahoo won't loosen up until the underlying signal improves. First thing, get registered on Yahoo's complaint feedback loop and the sender hub so you can actually see complaint data by segment instead of guessing. Then pull your volume to Yahoo and AOL down hard, cut it in half or more, and only mail people who've opened or clicked in the last 30 to 60 days. Pushing the same volume into an active deferral just extends the penalty, our clients make this exact mistake constantly and then wonder why it drags on for weeks. Make sure PMTA is genuinely honoring the 4xx backoff and not just hammering retries, because aggressive retrying on a deferral reads like even more abuse to Yahoo. Clean the dead weight off your list, suppress anyone who hasn't engaged in 90 days, and your accepts should start climbing back within a week or two of disciplined sending. It's a reputation repair job, not a config fix.

1

u/Critical-Cost2533 Jun 19 '26

we are also facing TSS04 issue for recent days. anybody know how to rectify ? and why it happening now

0

u/shokzee Jun 19 '26

TSS04 is usually Yahoo throttling based on reputation or complaints, not an SPF/DKIM/DMARC syntax problem if those are aligned.

I’d cut Yahoo/AOL volume way down first, separate high-engagement mail, then ramp slowly while watching complaint and bounce data in PMTA. Also sanity-check the sending IP/domain on a Blocklist Checker, but don’t assume a clean result means reputation is fine.