Paubox email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 18, 2026), Paubox is the email service provider (ESP) for 169 domains — 0.03% of 637,944 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 169 domains in the Tranco top-1M use Paubox (0.03% of SPF-publishing domains).
- Snapshot date: 2026-09-18 — recomputed every day.
- Strongest TLD: .com (78.1% of its domains).
- Most co-used service: Google Workspace.
- Directory category: email security gateway.
Why Paubox appears in this category
Paubox — HIPAA-compliant email gateway.
We classify it as a email security gateway 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.
Paubox is an email service provider that appears within email authentication records across the public web, identifiable through its SPF include mechanisms in domain DNS configurations.
Paubox's footprint skews toward smaller and mid-market organisations rather than the largest global brands, concentrating heavily within the .com namespace. The provider appears particularly often alongside Google Workspace, suggesting a complementary role within organisations that have already committed to modern cloud email platforms. For email professionals, this pattern signals that any infrastructure audit of a site receiving mail from a Paubox-aligned domain should account for the provider's presence in the sending ecosystem.
Where Paubox 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 | 20 | 11.8% |
| Top 1,000,000 | 149 | 88.2% |
| Unranked | 0 | 0.0% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 132 | 78.1% | |
| .org | 16 | 9.5% | |
| .net | 6 | 3.6% | |
| .ai | 5 | 3.0% | |
| .co | 2 | 1.2% | |
| .io | 2 | 1.2% | |
| .health | 1 | 0.6% | |
| .edu | 1 | 0.6% | |
| .md | 1 | 0.6% | |
| .vc | 1 | 0.6% |
What Paubox users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 169 domains.
| Type | Service | Domains | Share of Paubox users |
|---|---|---|---|
| Mailbox | Google Workspace | 74 | 43.8% |
| Mailbox | Microsoft 365 | 43 | 25.4% |
| Mailbox | Proofpoint | 11 | 6.5% |
| Mailbox | Generic / unmatched (mx*.*) | 11 | 6.5% |
| Mailbox | Mimecast | 8 | 4.7% |
| Mailbox | Unknown / Other | 5 | 3.0% |
| ESP | HubSpot | 47 | 27.8% |
| ESP | Salesforce | 40 | 23.7% |
| ESP | Zendesk | 30 | 17.8% |
| ESP | Amazon SES | 23 | 13.6% |
SPF and Paubox include mechanisms
When Paubox appears in an organisation's SPF record, it adds an additional authorised sender range to the domain's authentication posture. This is common practice for companies layering multiple email services atop their primary platform—often Google Workspace. When testing email authentication or diagnosing delivery issues, the presence of Paubox includes means that SPF validation will check against Paubox's published sender IP ranges in addition to the primary email provider's, and overlooking any included provider can result in false-positive SPF failures or incomplete authentication checks.
See the full Paubox 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 Paubox in an SPF record mean for email delivery?
Paubox is an email service provider authorised to send on behalf of that domain; when present in an SPF record, mail from Paubox IP ranges will pass SPF checks. If you are auditing delivery or authentication, verify that all SPF includes—including Paubox—are intentional and still in use.
How many domains use Paubox?
169 domains in the Tranco top-1M use Paubox as their email service provider (ESP) as of September 18, 2026 (0.03% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Paubox common enough to affect email deliverability testing?
Paubox accounts for 0.03% 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 Paubox most?
Paubox's largest TLD is .com (78.1% of its domains); it appears across 12 TLDs in total.