FSI (JP ISP) mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 13, 2026), FSI (JP ISP) is the mailbox provider for 256 domains — 0.04% of 664,797 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 256 domains in the Tranco top-1M use FSI (JP ISP) (0.04% of domains with MX records).
- Snapshot date: 2026-09-13 — recomputed every day.
- Strongest TLD: .jp (47.3% of its domains).
- Region skew: Japan.
- Most co-used service: FSI Email Security.
- Directory category: mailbox provider.
Why FSI (JP ISP) appears in this category
Japanese ISP mail (fsi.ne.jp).
We classify it as a mailbox provider from primary MX record (lowest preference) matching a maintained provider rule. This is infrastructure attribution from public DNS, not evidence of a direct contract or exclusive use.
FSI is a Japanese mailbox provider and ISP offering email hosting primarily to regional businesses and smaller-to-mid-market sites across the .jp domain space. It typically operates its own MX infrastructure and offers integrated email security features through FSI Email Security, a companion product suite.
FSI's presence in the MX record marks regional Japanese recipients; this distributed footprint across smaller sites means email senders rarely encounter FSI in volume, but those targeting Japan or Japanese-speaking businesses should verify authentication compliance with FSI's filtering standards, which tend to align with Japanese regulatory preferences and regional email practices.
Where FSI (JP ISP) sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 0 | 0.0% |
| Top 100,000 | 5 | 2.0% |
| Top 1,000,000 | 249 | 97.3% |
| Unranked | 2 | 0.8% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .jp | 121 | 47.3% | |
| .com | 83 | 32.4% | |
| .co.jp | 24 | 9.4% | |
| .net | 13 | 5.1% | |
| .shop | 9 | 3.5% | |
| .ne.jp | 4 | 1.6% | |
| .link | 1 | 0.4% | |
| .me | 1 | 0.4% |
What FSI (JP ISP) users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 256 domains.
| Type | Service | Domains | Share of FSI (JP ISP) users |
|---|---|---|---|
| ESP | FSI Email Security | 255 | 99.6% |
| ESP | Q-Send | 134 | 52.3% |
| ESP | Repica WebCAS | 11 | 4.3% |
| ESP | Amazon SES | 8 | 3.1% |
| ESP | BizMatrix | 5 | 2.0% |
| ESP | Zendesk | 3 | 1.2% |
| ESP | Tricorn | 2 | 0.8% |
| ESP | SendGrid (Twilio) | 1 | 0.4% |
| ESP | HubSpot | 1 | 0.4% |
| ESP | Mailchimp | 1 | 0.4% |
FSI Email Security and authentication compliance
FSI Email Security applies strict sender authentication checks, prioritising DMARC, SPF, and DKIM validation across all inbound messages. Campaigns targeting FSI-hosted recipients should ensure all three protocols are correctly deployed and aligned with the sending domain; FSI's regional focus and security posture mean that authentication failures or misalignment are flagged more aggressively than at some global providers, particularly for geographically distant senders.
See the full FSI (JP ISP) data page (KPI cards, trend, sample domains) →
Run a free inbox-placement test across Gmail, Outlook, Yahoo and more — see exactly where your mail lands and why.
Frequently asked questions
What is FSI and how does it affect email deliverability?
FSI is a Japanese ISP and mailbox provider serving regional businesses; its integrated FSI Email Security product enforces strict DMARC, SPF, and DKIM validation, requiring senders targeting Japanese recipients to ensure proper authentication alignment.
How many domains use FSI (JP ISP)?
256 domains in the Tranco top-1M use FSI (JP ISP) as their mailbox provider as of September 13, 2026 (0.04% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is FSI (JP ISP) common enough to affect email deliverability testing?
FSI (JP ISP) accounts for 0.04% of domains with MX records in the top 1M. Whether you should seed a test mailbox there depends on how much of your audience it represents — the co-usage table above shows the services it appears alongside most.
Which countries or TLDs use FSI (JP ISP) most?
FSI (JP ISP)'s largest TLD is .jp (47.3% of its domains); it appears across 8 TLDs in total.