Bullhorn email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 22, 2026), Bullhorn is the email service provider (ESP) for 104 domains — 0.02% of 637,585 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 104 domains in the Tranco top-1M use Bullhorn (0.02% of SPF-publishing domains).
- Snapshot date: 2026-09-22 — recomputed every day.
- Strongest TLD: .com (76.0% of its domains).
- Most co-used service: Microsoft 365.
- Directory category: email service provider.
Why Bullhorn appears in this category
Bullhorn — recruitment CRM with built-in email.
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.
Bullhorn is a talent management and customer relationship management platform that incorporates email capabilities for candidate outreach and pipeline communication. The service is provided by Bullhorn Inc., a cloud-based software company serving recruitment agencies, staffing firms, and talent-focused enterprises.
Bullhorn's SPF authentication footprint is concentrated in smaller organisations and the .com domain space, rather than appearing uniformly across enterprise-scale deployments. Its frequent co-occurrence with Microsoft 365 suggests a hybrid mail stack configuration where Bullhorn handles application-specific workflows—candidate notifications, job alerts, or process confirmations—whilst Microsoft 365 serves as the primary email platform. For mail receivers, the relative infrequency of Bullhorn-authenticated messages compared to major providers means they have accumulated less direct reputation history from Bullhorn sources, which can influence filtering approach and authentication signal interpretation.
Where Bullhorn 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 | 4.8% |
| Top 1,000,000 | 97 | 93.3% |
| Unranked | 2 | 1.9% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 79 | 76.0% | |
| .co.uk | 5 | 4.8% | |
| .com.au | 2 | 1.9% | |
| .nl | 2 | 1.9% | |
| .org | 2 | 1.9% | |
| .it | 1 | 1.0% | |
| .net | 1 | 1.0% | |
| .ie | 1 | 1.0% | |
| .bg | 1 | 1.0% | |
| .com.mx | 1 | 1.0% |
What Bullhorn users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 104 domains.
| Type | Service | Domains | Share of Bullhorn users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 60 | 57.7% |
| Mailbox | Mimecast | 15 | 14.4% |
| Mailbox | Google Workspace | 14 | 13.5% |
| Mailbox | Proofpoint | 7 | 6.7% |
| Mailbox | Cisco IronPort | 3 | 2.9% |
| Mailbox | Proofpoint Essentials | 2 | 1.9% |
| ESP | HubSpot | 46 | 44.2% |
| ESP | Salesforce | 27 | 26.0% |
| ESP | SendGrid (Twilio) | 20 | 19.2% |
| ESP | Amazon SES | 15 | 14.4% |
SPF configuration and reputation data in hybrid stacks
When Bullhorn is deployed alongside Microsoft 365, both providers' SPF mechanisms are typically included in the domain's authentication record. Mail receivers and ISPs accumulate reputation data separately for each authenticated source. Because Bullhorn mail is encountered less frequently than mail from dominant providers due to its concentration in smaller organisations, ISPs may have limited direct reputation history for Bullhorn-authenticated traffic, potentially resulting in less granular filtering rules or signal strength. Organisations using this hybrid configuration should monitor delivery performance and sender reputation across both authentication paths.
See the full Bullhorn data page (KPI cards, trend, sample domains) →
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Frequently asked questions
What is Bullhorn and why does it appear in my SPF record?
Bullhorn is a talent management platform with integrated email capabilities used by recruitment and staffing organisations for candidate communication and workflow-triggered mail. Its SPF include is added when you use Bullhorn's outreach features; since Bullhorn is primarily deployed by smaller organisations, mail receivers typically encounter it less frequently than major email providers.
How many domains use Bullhorn?
104 domains in the Tranco top-1M use Bullhorn as their email service provider (ESP) as of September 22, 2026 (0.02% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Bullhorn common enough to affect email deliverability testing?
Bullhorn accounts for 0.02% 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 Bullhorn most?
Bullhorn's largest TLD is .com (76.0% of its domains); it appears across 19 TLDs in total.