AuthSMTP email provider statistics and deliverability context
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According to Live Direct Marketing's daily Tranco top-1M scan (September 24, 2026), AuthSMTP is the email service provider (ESP) for 966 domains — 0.15% of 637,420 SPF-publishing domains. Its strongest TLD is .com (54.6% of its domains). Detection: include: mechanisms in the SPF record.
Last updated from the 2026-09-24 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 2026-09-24 snapshot shows about AuthSMTP
Across 59 distinct TLDs its top three are .com (54.6%), .co.uk (8.4%), .org (7.0%) — together 70.0% of the 966 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, 406 domains, 42.0% of them), followed by Google Workspace (21.0%). 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 (2026-09-24); 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 966 domains use — cross-tabulated from the same daily snapshot (2026-09-24).
| Type | Service | Domains | Share of AuthSMTP users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 406 | 42.0% |
| Mailbox | Google Workspace | 203 | 21.0% |
| Mailbox | Self-Hosted | 67 | 6.9% |
| Mailbox | Mimecast | 60 | 6.2% |
| Mailbox | Unknown / Other | 51 | 5.3% |
| Mailbox | Proofpoint | 24 | 2.5% |
| ESP | SendGrid (Twilio) | 118 | 12.2% |
| ESP | Amazon SES | 115 | 11.9% |
| ESP | Mailchimp | 97 | 10.0% |
| ESP | Zendesk | 97 | 10.0% |
TLD distribution (top 30 of 59)
Frequently asked questions
How many domains use AuthSMTP?
966 domains in the Tranco top-1M use AuthSMTP as their email service provider (ESP) as of September 24, 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 2026-09-24). 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 2026-09-24).
Largest email service provider (ESP)s in this category
Amazon SES (6.23%) · SendGrid (Twilio) (4.68%) · Mailgun (4.01%) · Zendesk (3.77%) · Mailchimp (3.61%) · Mandrill (3.26%) · HubSpot (3.18%) · Salesforce (2.57%) · Mailjet (Sinch) (2.14%) · Cloudflare Email Routing (1.96%)
Domain sample (top 100 by Tranco rank)
Showing 100 of 966 domains.