Why Your Sequences Die in Japan: The Email Stack You've Never Heard Of

Every outbound team that expands into Japan runs the same experiment: take the sequence that books meetings in the US and Europe, translate it, and watch it produce close to nothing. The usual explanations are cultural — and culture matters — but there is an infrastructure layer underneath that Western deliverability advice never mentions, because Western surveys never see it.

Our daily DNS scan of the Tranco top-1M classifies ESP usage per country by reading SPF records. In the 2026-04-28 regional slice of that dataset (scan running daily through the 2026-07-05 snapshot), Japan looks like nowhere else in the developed world.

Japan's ESP league table is not your ESP league table

Amazon SES at the top is the one familiar note — it is the global leader too. Everything after it diverges. SecureMX, the number two, is a name most Western deliverability consultants have never typed. And deeper in the dataset sits the striking part: Kagoya, MailWise, ActiveGate, Tricorn and CrmStyle each show a customer base that is 100% Japanese domains. These are not small players with a home bias; they are entire parallel ecosystems with zero overlap with the market your playbook was trained on. The full country-by-country breakdown is in the daily email infrastructure report.

Japan is the most extreme case of a broader pattern — France runs disproportionately on Mailjet, Brazil on Locaweb — which we map in the regional mail-stack guide. But nowhere else combines this degree of domestic isolation with this market size.

Why this kills Western sequences

• Your reputation capital does not transfer. Years of careful sending built you standing with Gmail and Microsoft. Domestic Japanese filters and receiving stacks have never seen your domain. You start from zero — often from below zero, since foreign-origin bulk mail is a known abuse pattern.
• The filters are tuned differently. Domestic receiving stacks weigh different signals than the engagement-driven models at Gmail. Domain-level trust of established local senders is high; unknown foreign infrastructure is treated with suspicion regardless of copy quality.
• Mobile carrier domains play by their own rules. A meaningful share of Japanese business contacts still use carrier mail addresses, and carrier-grade filtering has historically been among the strictest anywhere — domain-based allow-listing by recipients is a normal user behaviour there, not an edge case.
• Your tooling's assumptions break. Placement dashboards that seed-test only Gmail, Outlook and Yahoo tell you nothing about where mail lands behind a SecureMX- or Kagoya-hosted domain.

Format is a deliverability feature in Japan

Even when your mail arrives, a translated Western template reads as spam to the human. Japanese business email has strong conventions, and violating them is the fastest way to be deleted — or reported:

• Plain text wins. Japanese B2B email is overwhelmingly text-based, often with the traditional full-width formatting. HTML-heavy layouts with hero images signal "marketing blast," not correspondence.
• Identify yourself completely, immediately. Company, full name, and the reason for contact belong in the opening lines (and a full signature block with address is expected). The Western "pattern-interrupt" one-liner reads as evasive.
• Politeness register is binary. Correct keigo (honorific language) is table stakes; machine-translated casual English marks the message as foreign bulk instantly. Budget for a native writer, not a translator.
• Soft asks outperform hard CTAs. A request to be allowed to send more information typically outperforms a direct meeting ask on a first touch.

The upside of the closed stack: competition inside it is thin. Most foreign senders never adapt, so the ones who invest in local infrastructure knowledge, correct formatting, and measured sending stand out to Japanese buyers precisely because so little correctly crafted foreign outreach gets through.

FAQ