Turbo-SMTP email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 20, 2026), Turbo-SMTP is the email service provider (ESP) for 984 domains — 0.15% of 638,158 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 984 domains in the Tranco top-1M use Turbo-SMTP (0.15% of SPF-publishing domains).
- Snapshot date: 2026-09-20 — recomputed every day.
- Strongest TLD: .com (34.9% of its domains).
- Most co-used service: Microsoft 365.
- Directory category: email service provider.
Why Turbo-SMTP appears in this category
Italian SMTP relay service.
We classify it as a email service provider from include: mechanisms in the SPF record matching a maintained provider rule. This is infrastructure attribution from public DNS, not evidence of a direct contract or exclusive use.
Turbo-SMTP is an email service provider offering mail relay and sending services. It appears predominantly in the SPF records of smaller websites across international TLDs, and frequently co-exists with Microsoft 365 configurations.
Recipients will encounter Turbo-SMTP as sending infrastructure for smaller organisations across international markets, so should account for varied sender reputation profiles. Senders on Turbo-SMTP rely on individual authentication and list discipline, as reputation is distributed across the platform's diverse customer base.
Where Turbo-SMTP sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 4 | 0.4% |
| Top 100,000 | 88 | 8.9% |
| Top 1,000,000 | 887 | 90.1% |
| Unranked | 5 | 0.5% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 343 | 34.9% | |
| .it | 296 | 30.1% | |
| .de | 33 | 3.4% | |
| .org | 32 | 3.3% | |
| .net | 30 | 3.0% | |
| .fr | 28 | 2.8% | |
| .nl | 18 | 1.8% | |
| .co.uk | 12 | 1.2% | |
| .es | 11 | 1.1% | |
| .eu | 10 | 1.0% |
What Turbo-SMTP users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 984 domains.
| Type | Service | Domains | Share of Turbo-SMTP users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 294 | 29.9% |
| Mailbox | Self-Hosted | 200 | 20.3% |
| Mailbox | Google Workspace | 183 | 18.6% |
| Mailbox | Unknown / Other | 82 | 8.3% |
| Mailbox | Generic / unmatched (mx*.*) | 30 | 3.0% |
| Mailbox | Barracuda | 13 | 1.3% |
| ESP | Amazon SES | 84 | 8.5% |
| ESP | MailUp | 67 | 6.8% |
| ESP | Mailjet (Sinch) | 54 | 5.5% |
| ESP | Zendesk | 53 | 5.4% |
SPF record integration and long-tail adoption
Turbo-SMTP appears predominantly in SPF records of smaller domains across international TLDs, meaning recipients encounter it as legitimate sending infrastructure for non-enterprise organisations. As a shared relay platform, individual sender reputation depends on each sender's own authentication and list quality; recipients should account for the fact that sender reputation is not uniform across Turbo-SMTP's customer base but varies by individual sender practices.
See the full Turbo-SMTP 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 Turbo-SMTP and should I include it in deliverability testing?
Turbo-SMTP is a mail relay service deployed predominantly by smaller organisations, often alongside Microsoft 365. It is worth testing if your recipient base spans long-tail or international segments; as a non-mainstream provider, it should not be your sole test platform.
How many domains use Turbo-SMTP?
984 domains in the Tranco top-1M use Turbo-SMTP as their email service provider (ESP) as of September 20, 2026 (0.15% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Turbo-SMTP common enough to affect email deliverability testing?
Turbo-SMTP accounts for 0.15% 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.
Which countries or TLDs use Turbo-SMTP most?
Turbo-SMTP's largest TLD is .com (34.9% of its domains); it appears across 89 TLDs in total.