According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), Unknown / Other is the mailbox provider for 49,698 domains — 7.54% of 658,711 domains with MX records. Detection method: primary MX record (lowest preference).
Unknown / Other is the category assigned to mailbox providers that do not match known major services like Gmail, Microsoft 365, Proton Mail, or Apple Mail. This includes smaller email hosting services, custom mail server implementations, and organisations running their own infrastructure. The label reflects the diversity of smaller providers across global networks rather than a single entity or operator.
For senders, this category matters because it represents a fragmented landscape of receiving systems with varying levels of email configuration maturity. Recipients using these services may experience inconsistent filtering, authentication enforcement, and inbox placement depending on how well their particular provider implements industry standards. Marketers and systems administrators need to recognise that email destined for this broad set of providers faces a wider range of potential delivery challenges than mail to consolidated providers.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 62 | 0.1% |
| Top 10,000 | 480 | 1.0% |
| Top 100,000 | 4,750 | 9.6% |
| Top 1,000,000 | 36,870 | 74.2% |
| Unranked | 7,536 | 15.2% |
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 15,814 | 31.8% | |
| .de | 3,224 | 6.5% | |
| .net | 2,940 | 5.9% | |
| .org | 1,840 | 3.7% | |
| .ru | 1,629 | 3.3% | |
| .pl | 1,357 | 2.7% | |
| .jp | 1,255 | 2.5% | |
| .it | 1,032 | 2.1% | |
| .fr | 1,019 | 2.1% | |
| .nl | 952 | 1.9% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 49,698 domains.
| Type | Service | Domains | Share of Unknown / Other users |
|---|---|---|---|
| ESP | Amazon SES | 1,584 | 3.2% |
| ESP | SendGrid (Twilio) | 1,170 | 2.4% |
| ESP | Mailchimp | 1,073 | 2.2% |
| ESP | Mailjet (Sinch) | 967 | 1.9% |
| ESP | Mandrill | 919 | 1.8% |
| ESP | Zendesk | 919 | 1.8% |
| ESP | Mailgun | 908 | 1.8% |
| ESP | Salesforce | 648 | 1.3% |
| ESP | Trend Micro Email Security | 574 | 1.2% |
| ESP | Brevo (ex-Sendinblue) | 510 | 1.0% |
Since Unknown / Other comprises many independent or smaller-scale implementations, these mail servers show significant variation in how strictly they enforce authentication standards like SPF, DKIM, and DMARC. Some smaller providers may lack proper SPF configuration entirely, whilst others apply strict validation; this inconsistency means that sender reputation checks and alignment signals receive variable weight. When Unknown / Other is frequently paired with Amazon SES in data, it often reflects SMEs and startups using SES infrastructure but routing mail through their own domains — a configuration that succeeds only when the sender maintains rigorous authentication setup across all three protocols.
See the full Unknown / Other data page (KPI cards, trend, sample domains) →
Unknown / Other is a category for mailbox providers not identified as major services—smaller hosting platforms, custom implementations, and independent infrastructure. This category reflects the long tail of email infrastructure across diverse, fragmented receiving systems with varying levels of authentication and filtering enforcement.
49,698 domains in the Tranco top-1M use Unknown / Other as their mailbox provider as of July 13, 2026 (7.54% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Unknown / Other accounts for 7.54% of domains with MX records 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.
Unknown / Other is declining — its share moved -0.28 pp over the last 30 days (as of July 13, 2026).
Unknown / Other's largest TLD is .com (31.8% of its domains); it appears across 565 TLDs in total.