Retarus mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 20, 2026), Retarus is the mailbox provider for 119 domains — 0.02% of 676,114 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 119 domains in the Tranco top-1M use Retarus (0.02% of domains with MX records).
- Snapshot date: 2026-09-20 — recomputed every day.
- Strongest TLD: .de (39.5% of its domains).
- Region skew: Germany.
- Most co-used service: Retarus (DE gateway).
- Directory category: email security gateway.
Why Retarus appears in this category
German large-enterprise messaging services / email gateway.
We classify it as a email security gateway 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.
Retarus is a mailbox provider and email gateway operator based in Germany, offering inbound and outbound email services for organisations across multiple sectors and geographies, with particular strength in German-speaking regions.
Unlike megaproviders such as Microsoft or Google, Retarus predominantly hosts smaller and mid-market organisations rather than the largest global brands. Its European footprint, concentrated in German and neighbouring TLDs, means email practitioners sending to or receiving from Retarus-hosted domains often engage with regionally-diverse business entities. For senders targeting European markets, particularly Germany, Retarus represents a relevant testing point within regional compliance strategies rather than a universal baseline.
Where Retarus sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 1 | 0.8% |
| Top 100,000 | 25 | 21.0% |
| Top 1,000,000 | 93 | 78.2% |
| Unranked | 0 | 0.0% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .de | 47 | 39.5% | |
| .com | 34 | 28.6% | |
| .fr | 9 | 7.6% | |
| .at | 5 | 4.2% | |
| .ch | 4 | 3.4% | |
| .net | 2 | 1.7% | |
| .nl | 2 | 1.7% | |
| .eu | 2 | 1.7% | |
| .edu | 1 | 0.8% | |
| .hu | 1 | 0.8% |
What Retarus users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 119 domains.
| Type | Service | Domains | Share of Retarus users |
|---|---|---|---|
| ESP | Retarus (DE gateway) | 87 | 73.1% |
| ESP | IP Made (CDP) | 18 | 15.1% |
| ESP | Amazon SES | 7 | 5.9% |
| ESP | Mailjet (Sinch) | 6 | 5.0% |
| ESP | Salesforce Marketing Cloud | 6 | 5.0% |
| ESP | Salesforce | 6 | 5.0% |
| ESP | Brevo (ex-Sendinblue) | 5 | 4.2% |
| ESP | Mandrill | 5 | 4.2% |
| ESP | Zendesk | 4 | 3.4% |
| ESP | Constant Contact | 4 | 3.4% |
Regional Importance in European Email Testing
Retarus's concentration in smaller and mid-market European organisations, particularly in Germany and adjacent regions, makes it a relevant testing point for campaigns targeting those markets. However, because it does not represent global megaproviders or consumer segments, it should be tested as a regional priority alongside broader provider coverage rather than treated as a universal compliance baseline.
See the full Retarus data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Should I test email deliverability against Retarus?
Test against Retarus if targeting German-speaking markets or mid-market European organisations. Because it hosts smaller organisations rather than major consumer segments, it is a regional priority rather than a global compliance requirement.
How many domains use Retarus?
119 domains in the Tranco top-1M use Retarus as their mailbox provider as of September 20, 2026 (0.02% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is Retarus common enough to affect email deliverability testing?
Retarus accounts for 0.02% 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.
Which countries or TLDs use Retarus most?
Retarus's largest TLD is .de (39.5% of its domains); it appears across 22 TLDs in total.