SMTP.com email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 18, 2026), SMTP.com is the email service provider (ESP) for 1,567 domains — 0.25% of 637,944 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 1,567 domains in the Tranco top-1M use SMTP.com (0.25% of SPF-publishing domains).
- Snapshot date: 2026-09-18 — recomputed every day.
- Strongest TLD: .com (60.9% of its domains).
- Most co-used service: Microsoft 365.
- Directory category: email service provider.
Why SMTP.com appears in this category
Long-running US SMTP relay service for marketers.
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.
SMTP.com is an email service provider offering SMTP relay services to organisations that need to delegate outbound email sending to a third party. It is positioned as a specialist relay solution, allowing senders to outsource mail delivery or distribute sending load across multiple providers.
The presence of SMTP.com in SPF records is concentrated among smaller organisations and .com domains, often appearing alongside Microsoft 365 in hybrid mail environments. This pattern suggests SMTP.com serves as a supplementary relay for organisations managing mail across multiple platforms, and its footprint indicates a niche but established position within email infrastructure.
Where SMTP.com sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 2 | 0.1% |
| Top 10,000 | 11 | 0.7% |
| Top 100,000 | 154 | 9.8% |
| Top 1,000,000 | 1,385 | 88.4% |
| Unranked | 15 | 1.0% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 955 | 60.9% | |
| .org | 116 | 7.4% | |
| .co.uk | 66 | 4.2% | |
| .net | 52 | 3.3% | |
| .ca | 41 | 2.6% | |
| .org.uk | 32 | 2.0% | |
| .nl | 21 | 1.3% | |
| .de | 19 | 1.2% | |
| .com.au | 14 | 0.9% | |
| .fr | 11 | 0.7% |
What SMTP.com users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 1,567 domains.
| Type | Service | Domains | Share of SMTP.com users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 464 | 29.6% |
| Mailbox | Google Workspace | 458 | 29.2% |
| Mailbox | Self-Hosted | 143 | 9.1% |
| Mailbox | Mimecast | 77 | 4.9% |
| Mailbox | Unknown / Other | 61 | 3.9% |
| Mailbox | Proofpoint | 33 | 2.1% |
| ESP | Amazon SES | 199 | 12.7% |
| ESP | Zendesk | 158 | 10.1% |
| ESP | SendGrid (Twilio) | 149 | 9.5% |
| ESP | Mailgun | 114 | 7.3% |
Shared reputation and sender monitoring on SMTP.com
SMTP.com operates as a shared SMTP relay, meaning your sender reputation sits alongside that of its other customers. Organisations using SMTP.com should actively monitor delivery metrics, feedback loops, and spam complaint rates reported by the platform. Proper SPF, DKIM, and DMARC alignment is essential to separate your reputation signals from the broader customer base and to flag any negative feedback that may originate from other senders on the platform.
See the full SMTP.com 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 does it mean if SMTP.com appears in my SPF record?
SMTP.com in your SPF record indicates you are delegating SMTP sending to their service. This is typical for organisations using a dedicated email relay, and your sender reputation becomes partially shared with their platform; you should monitor delivery reports to ensure your sending is not adversely affected by other customers' behaviour.
How many domains use SMTP.com?
1,567 domains in the Tranco top-1M use SMTP.com as their email service provider (ESP) as of September 18, 2026 (0.25% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is SMTP.com common enough to affect email deliverability testing?
SMTP.com accounts for 0.25% 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 SMTP.com most?
SMTP.com's largest TLD is .com (60.9% of its domains); it appears across 110 TLDs in total.