1&1 IONOS mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 16, 2026), 1&1 IONOS is the mailbox provider for 4,564 domains — 0.68% of 672,143 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 4,564 domains in the Tranco top-1M use 1&1 IONOS (0.68% of domains with MX records).
- Snapshot date: 2026-09-16 — recomputed every day.
- 30-day share change: +0.03 pp.
- Strongest TLD: .com (41.7% of its domains).
- Region skew: Global / US-skewed.
- Most co-used service: Mailjet (Sinch).
- Directory category: hosting mail bundle.
Why 1&1 IONOS appears in this category
1&1 IONOS — Europe's largest hosting brand, bundled mail for SMB.
We classify it as a hosting mail bundle from primary MX record (lowest preference) matching a maintained provider rule. This is infrastructure attribution from public DNS, not evidence of a direct contract or exclusive use.
1&1 IONOS is a German web hosting, domain registration, and mailbox provider serving a globally distributed customer base. The company offers email hosting services primarily to smaller businesses and domain owners, with significant international presence.
In the email deliverability landscape, 1&1 IONOS occupies a middle position: its footprint is concentrated in the long tail of smaller websites rather than the largest brands, and its customers are internationally distributed across many TLDs, predominantly .com domains. The provider's increasing market share has raised its relevance for senders assessing sender reputation and authentication practices across diverse, geographically scattered audiences.
Where 1&1 IONOS sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 7 | 0.2% |
| Top 100,000 | 144 | 3.2% |
| Top 1,000,000 | 4,320 | 94.7% |
| Unranked | 93 | 2.0% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 1,904 | 41.7% | |
| .de | 1,041 | 22.8% | |
| .co.uk | 282 | 6.2% | |
| .fr | 244 | 5.3% | |
| .org | 224 | 4.9% | |
| .net | 190 | 4.2% | |
| .es | 131 | 2.9% | |
| .info | 55 | 1.2% | |
| .eu | 54 | 1.2% | |
| .org.uk | 32 | 0.7% |
What 1&1 IONOS users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 4,564 domains.
| Type | Service | Domains | Share of 1&1 IONOS users |
|---|---|---|---|
| ESP | Mailjet (Sinch) | 155 | 3.4% |
| ESP | Brevo (ex-Sendinblue) | 82 | 1.8% |
| ESP | Mailgun | 76 | 1.7% |
| ESP | Amazon SES | 65 | 1.4% |
| ESP | Mandrill | 44 | 1.0% |
| ESP | Mailchimp | 43 | 0.9% |
| ESP | Zendesk | 42 | 0.9% |
| ESP | MailerLite | 38 | 0.8% |
| ESP | Constant Contact | 36 | 0.8% |
| ESP | SendGrid (Twilio) | 35 | 0.8% |
Testing against 1&1 IONOS: what secondary-provider performance signals
1&1 IONOS's concentration in the long tail and its international footprint make it a useful secondary-provider benchmark in testing matrices. Because 1&1 IONOS's customers span many countries, regions, and TLDs rather than being clustered within the major consolidated platforms, performance against 1&1 IONOS mailboxes provides signal about sender reputation and authentication stance amongst a geographically dispersed, smaller-scale recipient base. Senders can use 1&1 IONOS results as an indicator of how their email will perform beyond the top-tier providers.
See the full 1&1 IONOS data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Should I test email delivery against 1&1 IONOS mailboxes?
Yes, if your audience includes smaller businesses across international markets; 1&1 IONOS's concentration in the long tail and growing market share make it a valuable inclusion in sender testing matrices.
How many domains use 1&1 IONOS?
4,564 domains in the Tranco top-1M use 1&1 IONOS as their mailbox provider as of September 16, 2026 (0.68% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is 1&1 IONOS common enough to affect email deliverability testing?
1&1 IONOS accounts for 0.68% 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.
Is 1&1 IONOS growing or declining?
1&1 IONOS is growing — its share moved +0.03 pp over the last 30 days (as of September 16, 2026).
Which countries or TLDs use 1&1 IONOS most?
1&1 IONOS's largest TLD is .com (41.7% of its domains); it appears across 116 TLDs in total.