AuthSMTP email provider statistics and deliverability context
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According to Live Direct Marketing's daily Tranco top-1M scan (September 11, 2026), AuthSMTP is the email service provider (ESP) for 954 domains — 0.15% of 631,089 SPF-publishing domains. Its strongest TLD is .com (55.1% of its domains). Detection: include: mechanisms in the SPF record.
Last updated from the 2026-09-11 DNS snapshot.
What AuthSMTP represents in this dataset
UK SMTP relay for SMB outbound.
Directory category: Esp. 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 2026-09-11 snapshot shows about AuthSMTP
Across 58 distinct TLDs its top three are .com (55.1%), .co.uk (8.3%), .org (6.7%) — together 70.1% of the 954 domains, which makes the footprint narrow — three TLDs cover most of it, which is typical of a regional or single-market operator. The service most often observed on the same domains is Microsoft 365 (Mailbox, 398 domains, 41.7% of them), followed by Google Workspace (20.9%). 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 (2026-09-11); 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 AuthSMTP
What else the same 954 domains use — cross-tabulated from the same daily snapshot (2026-09-11).
| Type | Service | Domains | Share of AuthSMTP users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 398 | 41.7% |
| Mailbox | Google Workspace | 199 | 20.9% |
| Mailbox | Self-Hosted | 68 | 7.1% |
| Mailbox | Mimecast | 58 | 6.1% |
| Mailbox | Unknown / Other | 52 | 5.5% |
| Mailbox | Proofpoint | 23 | 2.4% |
| ESP | Amazon SES | 118 | 12.4% |
| ESP | SendGrid (Twilio) | 111 | 11.6% |
| ESP | Mailchimp | 95 | 10.0% |
| ESP | Zendesk | 95 | 10.0% |
TLD distribution (top 30 of 58)
Frequently asked questions
How many domains use AuthSMTP?
954 domains in the Tranco top-1M use AuthSMTP as their email service provider (ESP) as of September 11, 2026, according to Live Direct Marketing's daily DNS scan.
What is AuthSMTP's market share?
AuthSMTP holds 0.15% of SPF-publishing domains in the Tranco top-1M (snapshot of 2026-09-11). The number is recomputed every day.
What are the biggest alternatives to AuthSMTP?
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 2026-09-11).
Largest email service provider (ESP)s in this category
Amazon SES (6.17%) · SendGrid (Twilio) (4.63%) · Mailgun (4.00%) · Zendesk (3.76%) · Mailchimp (3.56%) · Mandrill (3.24%) · HubSpot (3.10%) · Salesforce (2.54%) · Mailjet (Sinch) (2.12%) · Cloudflare Email Routing (1.93%)
Domain sample (top 100 by Tranco rank)
Showing 100 of 954 domains.