According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), FSI Email Security is the email service provider (ESP) for 594 domains — 0.10% of 617,702 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
FSI Email Security is an email service provider operated by FSI, a Japanese internet service provider, serving primarily small and mid-sized organisations across multiple geographic regions. It is typically encountered as an SPF include mechanism within domain authentication records, particularly across sites in the .jp namespace and distributed internationally.
For deliverability and infrastructure professionals, FSI Email Security's significance lies in its distributed, long-tail footprint. Rather than representing a major consolidated platform, it serves numerous smaller organisations globally, with strongest presence in Japan. This means that encountering FSI in SPF records is rarely indicative of sender reputation issues—problems are typically organisation-specific rather than provider-wide.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 2 | 0.3% |
| Top 100,000 | 19 | 3.2% |
| Top 1,000,000 | 472 | 79.5% |
| Unranked | 101 | 17.0% |
| TLD | Domains | Share | |
|---|---|---|---|
| .jp | 209 | 35.2% | |
| .com | 179 | 30.1% | |
| .co.jp | 143 | 24.1% | |
| .net | 20 | 3.4% | |
| .ne.jp | 8 | 1.3% | |
| .shop | 8 | 1.3% | |
| .or.jp | 8 | 1.3% | |
| .ac.jp | 6 | 1.0% | |
| .org | 3 | 0.5% | |
| .coop | 2 | 0.3% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 594 domains.
| Type | Service | Domains | Share of FSI Email Security users |
|---|---|---|---|
| Mailbox | FSI (JP ISP) | 251 | 42.3% |
| Mailbox | Self-Hosted | 84 | 14.1% |
| Mailbox | Google Workspace | 73 | 12.3% |
| Mailbox | Unknown / Other | 51 | 8.6% |
| Mailbox | Microsoft 365 | 50 | 8.4% |
| Mailbox | Kagoya (JP) | 14 | 2.4% |
| ESP | Q-Send | 178 | 30.0% |
| ESP | Repica WebCAS | 47 | 7.9% |
| ESP | Amazon SES | 46 | 7.7% |
| ESP | BizMatrix | 28 | 4.7% |
FSI Email Security's role in email authentication is primarily visible through SPF include directives, where organisations authorise it to send mail on their behalf. Its prominence in Japanese domains reflects its regional foundation, whilst its presence across other international markets indicates adoption by small businesses and nonprofits worldwide. For infrastructure teams evaluating authentication records, FSI SPF includes present no inherent deliverability risk unless the authorising domain itself carries poor reputation or has authentication configuration flaws.
See the full FSI Email Security data page (KPI cards, trend, sample domains) →
Testing is not necessary for most senders unless you specifically use FSI Email Security as your outbound mail provider or suspect delivery problems to FSI-affiliated organisations. Deliverability issues are typically organisation-specific rather than provider-wide.
594 domains in the Tranco top-1M use FSI Email Security as their email service provider (ESP) as of July 13, 2026 (0.10% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
FSI Email Security accounts for 0.10% of SPF-publishing domains 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.
FSI Email Security's largest TLD is .jp (35.2% of its domains); it appears across 18 TLDs in total.