CSOF (DE) mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 10, 2026), CSOF (DE) is the mailbox provider for 474 domains — 0.07% of 667,099 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 474 domains in the Tranco top-1M use CSOF (DE) (0.07% of domains with MX records).
- Snapshot date: 2026-09-10 — recomputed every day.
- Strongest TLD: .com (43.7% of its domains).
- Region skew: Global / US-skewed.
- Most co-used service: Mailspike.
- Directory category: hosting mail bundle.
Why CSOF (DE) appears in this category
Niche German hosting (Computer Service Online Folkesund).
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.
CSOF (DE) is a mailbox provider—a mail-hosting service that manages inbound and outbound mail infrastructure. It serves a global customer base with a slight US skew, concentrated predominantly in the .com namespace.
Because CSOF (DE) sits in the long tail of smaller websites rather than among the largest brands, mainstream senders encounter it less frequently; however, it remains relevant for smaller campaigns and niche verticals. Its frequent pairing with Mailspike, a third-party mail reputation service, suggests customers often layer additional email management atop base hosting, which can affect how authentication and feedback signals flow.
Where CSOF (DE) sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 0 | 0.0% |
| Top 100,000 | 14 | 3.0% |
| Top 1,000,000 | 447 | 94.3% |
| Unranked | 13 | 2.7% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 207 | 43.7% | |
| .net | 54 | 11.4% | |
| .biz | 33 | 7.0% | |
| .fr | 11 | 2.3% | |
| .one | 9 | 1.9% | |
| .in | 8 | 1.7% | |
| .online | 8 | 1.7% | |
| .top | 8 | 1.7% | |
| .site | 7 | 1.5% | |
| .co.uk | 7 | 1.5% |
What CSOF (DE) users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 474 domains.
| Type | Service | Domains | Share of CSOF (DE) users |
|---|---|---|---|
| ESP | Mailspike | 467 | 98.5% |
Mailspike Co-Deployment and Authentication Paths
When CSOF (DE) is deployed alongside Mailspike, responsibility for SPF, DKIM, and DMARC records—and for bounce handling and complaint feedback—may be split between the two services. Senders should verify which platform owns DNS configuration and which receives feedback loops to avoid conflicts or missed signals during troubleshooting.
See the full CSOF (DE) data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Should I test email deliverability against CSOF (DE)?
Yes, if your audience includes smaller .com sites or niches where CSOF (DE) is deployed. Since it occupies the long tail rather than mainstream carriers, prioritise larger providers first unless you have direct evidence your actual recipients use it.
How many domains use CSOF (DE)?
474 domains in the Tranco top-1M use CSOF (DE) as their mailbox provider as of September 10, 2026 (0.07% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is CSOF (DE) common enough to affect email deliverability testing?
CSOF (DE) accounts for 0.07% 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 CSOF (DE) most?
CSOF (DE)'s largest TLD is .com (43.7% of its domains); it appears across 70 TLDs in total.