According to Live Direct Marketing's daily Tranco top-1M scan (July 12, 2026), AuthSMTP is the email service provider (ESP) for 957 domains — 0.15% of 617,244 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
AuthSMTP is an email service provider that senders authorise through SPF include mechanisms. It facilitates outbound mail for customers across various sectors, with its usage declared in sending domain SPF records.
AuthSMTP's footprint sits predominantly in the long tail of medium-to-small websites rather than among the largest global brands, with strong concentration in the .com namespace. It frequently appears alongside Microsoft 365 configurations, suggesting adoption among SMBs and enterprises running hybrid mail environments. For senders and recipients alike, this means AuthSMTP-authorised mail originates from a diverse, distributed set of smaller domains rather than from a small number of heavily-trafficked senders.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 1 | 0.1% |
| Top 10,000 | 21 | 2.2% |
| Top 100,000 | 142 | 14.8% |
| Top 1,000,000 | 722 | 75.4% |
| Unranked | 71 | 7.4% |
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 533 | 55.7% | |
| .co.uk | 76 | 7.9% | |
| .org | 66 | 6.9% | |
| .nl | 56 | 5.9% | |
| .es | 24 | 2.5% | |
| .net | 22 | 2.3% | |
| .org.uk | 18 | 1.9% | |
| .com.au | 17 | 1.8% | |
| .ca | 13 | 1.4% | |
| .it | 12 | 1.3% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 957 domains.
| Type | Service | Domains | Share of AuthSMTP users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 403 | 42.1% |
| Mailbox | Google Workspace | 207 | 21.6% |
| Mailbox | Self-Hosted | 63 | 6.6% |
| Mailbox | Mimecast | 56 | 5.9% |
| Mailbox | Unknown / Other | 53 | 5.5% |
| Mailbox | Proofpoint | 21 | 2.2% |
| ESP | Amazon SES | 114 | 11.9% |
| ESP | SendGrid (Twilio) | 113 | 11.8% |
| ESP | Zendesk | 96 | 10.0% |
| ESP | Mailchimp | 95 | 9.9% |
AuthSMTP's concentrated presence on smaller domains means senders authorising it do not inherit reputation from large, high-volume senders. This distributes AuthSMTP's reputation signal across many smaller sources rather than concentrating it; consequently, senders should prioritise domain-level authentication (DKIM and DMARC) and list hygiene as more reliable deliverability levers than SPF alone.
See the full AuthSMTP data page (KPI cards, trend, sample domains) →
If you are not using AuthSMTP to send mail, its presence in SPF records has no direct impact on your deliverability. If you do use it, prioritise DKIM and DMARC authentication and sender reputation rather than relying on SPF alone.
957 domains in the Tranco top-1M use AuthSMTP as their email service provider (ESP) as of July 12, 2026 (0.15% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
AuthSMTP accounts for 0.15% 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.
AuthSMTP's largest TLD is .com (55.7% of its domains); it appears across 62 TLDs in total.