Microsoft Defender for Office 365 email provider statistics and deliverability context
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According to Live Direct Marketing's daily Tranco top-1M scan (September 14, 2026), Microsoft Defender for Office 365 is the email service provider (ESP) for 161 domains — 0.03% of 637,677 SPF-publishing domains. Its strongest TLD is .com (46.6% of its domains). Detection: include: mechanisms in the SPF record.
Last updated from the 2026-09-14 DNS snapshot.
What Microsoft Defender for Office 365 represents in this dataset
Microsoft 365 EOP / Defender — primary M365 mail security.
Directory category: Gateway. The classification comes from include: mechanisms in the SPF record. It describes observed DNS infrastructure, not a commercial relationship and not the placement of any individual message.
What the 2026-09-14 snapshot shows about Microsoft Defender for Office 365
Across 39 distinct TLDs its top three are .com (46.6%), .co.uk (6.2%), .org (6.2%) — together 59.0% of the 161 domains, which makes the footprint moderately concentrated, with a recognisable home market. The service most often observed on the same domains is Microsoft 365 (Mailbox, 78 domains, 48.4% of them), followed by Proofpoint (11.8%). Directly comparable by the same detection rule: Amazon SES, SendGrid (Twilio), Mailgun. Ranking between them reflects what is published in DNS, not delivery quality or volume sent. All figures come from a single daily DNS snapshot (2026-09-14); a domain appears here when its published records match the include: mechanisms in the SPF record rule, which is an infrastructure fact, not a commercial relationship.
Commonly used together with Microsoft Defender for Office 365
What else the same 161 domains use — cross-tabulated from the same daily snapshot (2026-09-14).
| Type | Service | Domains | Share of Microsoft Defender for Office 365 users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 78 | 48.4% |
| Mailbox | Proofpoint | 19 | 11.8% |
| Mailbox | Mimecast | 17 | 10.6% |
| Mailbox | Unknown / Other | 13 | 8.1% |
| Mailbox | Self-Hosted | 10 | 6.2% |
| Mailbox | Cisco IronPort | 6 | 3.7% |
| ESP | Mimecast | 18 | 11.2% |
| ESP | Proofpoint | 16 | 9.9% |
| ESP | Salesforce | 16 | 9.9% |
| ESP | Mandrill | 15 | 9.3% |
TLD distribution (top 30 of 39)
Frequently asked questions
How many domains use Microsoft Defender for Office 365?
161 domains in the Tranco top-1M use Microsoft Defender for Office 365 as their email service provider (ESP) as of September 14, 2026, according to Live Direct Marketing's daily DNS scan.
What is Microsoft Defender for Office 365's market share?
Microsoft Defender for Office 365 holds 0.03% of SPF-publishing domains in the Tranco top-1M (snapshot of 2026-09-14). The number is recomputed every day.
What are the biggest alternatives to Microsoft Defender for Office 365?
The largest email service provider (ESP)s in the same category by Tranco top-1M share are: Amazon SES, SendGrid (Twilio), Mailgun, Zendesk, Mailchimp (as of 2026-09-14).
Largest email service provider (ESP)s in this category
Amazon SES (6.16%) · SendGrid (Twilio) (4.62%) · Mailgun (4.00%) · Zendesk (3.75%) · Mailchimp (3.57%) · Mandrill (3.24%) · HubSpot (3.11%) · Salesforce (2.54%) · Mailjet (Sinch) (2.12%) · Cloudflare Email Routing (1.95%)
Domain sample (top 100 by Tranco rank)
Showing 100 of 161 domains.