Nine deliverability checks before the next solo send

Answer Before the next solo ad goes, check nine things Unspam collected on October 9, 2026 from a session with Matthew Vernhout of Email Industries. The old Gmail reputation score is gone. A DMARC record can now mean something harsher than the person who published it intended. Comcast is sliding toward Yahoo's filters. Ask the seller where their domain stands on each, in writing.

The note that started this: 2026 Email Deliverability Review: 9 Changes to Fix Before 2027, Andrian Valeanu, Unspam, October 9, 2026.

Andrian Valeanu's review is the note that started this. It recaps an October 8 webinar. The nine changes are in a table at the top. What follows is that table turned into questions a buyer can send and a seller can answer without a conference. The political-sender item barely touches a commercial solo. The other eight can decide whether Tuesday's mail exists.

What nine changes does Unspam's October 9 review name?

Postmaster Tools v1 retired, the Heatwave blocklist, new DMARC tags, removed DMARC tags, DKIM2 on the way, Gmail's political sender program, Gmail's AI inbox, subdomains judged with the root domain, and Comcast mail moving toward Yahoo's filters.

Take them in desk order.

• Postmaster Tools v1 is retired. Reputation labels, the old exports, and the v1 API are gone. v2 shows compliance: authentication, one-click unsubscribe, user-reported spam. It does not hand you a High or a Bad. A screenshot of a High domain reputation is a relic. Ask for a compliance view with a date, or stop pretending the relic is proof.
• Validity's Heatwave blocklist, launched September 3, 2026, targets domains warmed with fake engagement. Mail between accounts a tool controls, opened and rescued from spam by the tool, so a young domain looks loved. If a seller "warmed" the domain that will send your solo, ask whether that warming was people or software. A listing there is a bad week you paid to join.
• DMARC, republished as RFC 9989, adds tags. The review highlights np for subdomains that do not exist, psd for where the organization starts, and t as a test mode. A seller does not need a lecture. They need a record that matches what they think it does.
• The same republication drops pct, ri, and rf. A record that says p=reject; pct=25 used to reject a quarter of failing mail. A receiver following the new document rejects all of it. If the seller's safety feeling lives inside pct, it is time to feel something else and edit the record.
• DKIM2 is a draft, not a rule you must satisfy on Monday. The review says it is aimed at replay and at mailing lists that break signatures, and that 2027 is when it starts to matter. Ask the sending platform if it is on their roadmap. Then go back to the signature you need this week, which is still the DKIM you already have, at a key length the platform will actually use. The review passes along Vernhout's advice that 2048-bit is the size to ask for, and that 512-bit should not be in use.
• Gmail's verified sender program for US political committees opened September 8, 2026. The review is plain that nothing changes for any other sender. If you are not that sender, do not buy a story about a new Gmail badge.
• Gmail's AI inbox sorts and summarizes. A summary can only describe text that exists. An image-only email gives the model little to say. Put real sentences in the solo, and alt text on the images, so a summary has a chance of matching the offer. Vernhout's point, via the review, is also that Primary, Promotions, and the other tabs are all the inbox. Chasing Primary with a trick is a short hobby.
• Gmail judges a domain and its subdomains together. A pretty marketing subdomain with a perfect unsubscribe does not shield a root domain that keeps mailing people who left. One suppression list for every tool that sends under the name. The review repeats a figure from Unspam's tests: 14 percent passed the one-click List-Unsubscribe check. Most programs still fail the header. A solo seller who passes it should say so.
• Comcast mailboxes are moving onto Yahoo's filtering, addresses still @comcast.net. Yahoo trouble travels with them. If your last solos died at Yahoo, ask the seller what share of the file is Comcast, Yahoo, and AOL before you add another.

What should a solo ad buyer do about the old Gmail reputation score?

Stop accepting a High or Medium reputation screenshot as current proof. Unspam's October 9 review says Postmaster Tools v1 and those reputation scores are gone, and v2 reports compliance instead.

This is the check that catches a faded pitch deck. The slide was honest in 2024. It is a costume now. Replace it with four current facts: SPF, DKIM, and DMARC on the domain that will send; the one-click unsubscribe on the message; a complaint habit the seller will describe in words; and the mailbox mix, including the cable domains that are becoming Yahoo's problem. Those four fit in an email. A seller who runs a real list can answer them in an email. You are allowed to wait for the reply before you pay.

The review also says v2's data covers personal Gmail, the gmail.com and googlemail.com addresses, and does not describe a company's Google Workspace mail. A B2B-heavy file can look empty in Postmaster even when the mail is flowing to work inboxes. Ask which audience the screenshot, if they send one, is even about.

Which of the nine can a buyer ask about in one email?

Ask for the sending domain, a DMARC record without the old pct tag, one-click unsubscribe, whether any warming tool touched the domain, and what share of the list is Yahoo, AOL, or Comcast.

That is five lines. It covers the relic dashboard, the pct trap, the header almost nobody passes, the warming list, and the Yahoo migration. It leaves DKIM2 and the political program for a year when they are your problem. It leaves the AI inbox as a writing task you control: sentences, not a poster.

If you sell the send, answer the five lines in the quote template so the buyer does not have to invent them. Then do the part they cannot see. One suppression list. A DMARC record you would still recognize after RFC 9989. No synthetic warming on the domain you mail from. A Comcast and Yahoo count you could defend. The safe solo ads sellers page is the short version of that posture. This note is the 2026 appendix.

Vernhout's closing plan in the review has four steps for 2027: edit the DMARC record, move any tooling onto Postmaster v2, keep complaints under 0.1 percent and never over 0.3, and recalibrate for Yahoo and Comcast. The 60-day sunset he shows on a slide is, in the review's Q&A, a starting point for a program already in trouble. A daily sender might use about 30 days without engagement. A monthly sender might use much longer. A paying subscriber stays. Steal the principle, and set the window from how often you mail. Then, when someone wants to solo ads for affiliate marketing onto that list, you are renting them the live readers, which is the only rental that survives the nine changes.