According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), Signature365 is the email service provider (ESP) for 125 domains — 0.02% of 617,702 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Signature365 is an email service provider that issues SPF include mechanisms, allowing organisations to delegate portions of their email authentication to Signature365-managed infrastructure. Its deployment pattern shows prevalence among smaller and mid-market websites across many top-level domains, rather than concentration among the largest global brands.
For senders and administrators, Signature365's SPF footprint signals participation in email routing or relay operations; understanding where Signature365 appears in authentication records helps deliverability teams diagnose SPF misconfigurations and trace authorised mail sources. For mail receivers, recognising Signature365 as a legitimate ESP component (particularly in organisations that also use Microsoft 365) supports accurate authentication validation and reduces the risk of false-positive spam filtering.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 0 | 0.0% |
| Top 100,000 | 9 | 7.2% |
| Top 1,000,000 | 106 | 84.8% |
| Unranked | 10 | 8.0% |
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 55 | 44.0% | |
| .de | 11 | 8.8% | |
| .dk | 10 | 8.0% | |
| .nl | 8 | 6.4% | |
| .ch | 7 | 5.6% | |
| .be | 7 | 5.6% | |
| .org | 5 | 4.0% | |
| .eu | 3 | 2.4% | |
| .in | 3 | 2.4% | |
| .pl | 3 | 2.4% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 125 domains.
| Type | Service | Domains | Share of Signature365 users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 95 | 76.0% |
| Mailbox | Unknown / Other | 12 | 9.6% |
| Mailbox | Cisco IronPort | 4 | 3.2% |
| Mailbox | Hornetsecurity | 4 | 3.2% |
| Mailbox | Proofpoint | 3 | 2.4% |
| Mailbox | Generic / unmatched (mx*.*) | 1 | 0.8% |
| ESP | Mailjet (Sinch) | 17 | 13.6% |
| ESP | Zendesk | 14 | 11.2% |
| ESP | Mailchimp | 14 | 11.2% |
| ESP | HubSpot | 12 | 9.6% |
Signature365 frequently appears in SPF records for organisations using Microsoft 365, indicating hybrid email infrastructure where mail routing spans multiple providers. Misconfiguration—such as omitting Signature365's IP ranges when it handles legitimate mail, or exceeding SPF's include limit—can cause authentication failures. Both senders and receivers benefit from auditing SPF records to ensure Signature365 includes are necessary, correctly ordered, and actually authorised by the domain operator.
See the full Signature365 data page (KPI cards, trend, sample domains) →
Yes; Signature365 is a legitimate email service provider commonly used in Microsoft 365 environments for mail routing. Its SPF includes are safe to recognise when they appear in domain configurations you trust.
125 domains in the Tranco top-1M use Signature365 as their email service provider (ESP) as of July 13, 2026 (0.02% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Signature365 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.
Signature365's largest TLD is .com (44.0% of its domains); it appears across 21 TLDs in total.