CSC (corporate) mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 24, 2026), CSC (corporate) is the mailbox provider for 473 domains — 0.07% of 675,489 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 473 domains in the Tranco top-1M use CSC (corporate) (0.07% of domains with MX records).
- Snapshot date: 2026-09-24 — recomputed every day.
- Strongest TLD: .com (40.6% of its domains).
- Region skew: Global / US-skewed.
- Most co-used service: Amazon SES.
- Directory category: corporate mail infrastructure.
Why CSC (corporate) appears in this category
CSC Digital Brand Services — corporate registrar.
We classify it as a corporate mail infrastructure 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.
CSC is a corporate mailbox service deployed across thousands of smaller and mid-market websites, appearing as the primary MX record in their DNS. Its global footprint spans diverse country-code and commercial top-level domains, with particular concentration in .com registrations.
For email senders, CSC's presence in the long tail of the website landscape—rather than amongst the largest brands—makes it a useful deliverability reference point when targeting small-and-medium-sized organisations. The frequent co-appearance of SendGrid in these organisations' DNS records reflects a common pattern: CSC-hosted corporate email paired with specialist transactional services for customer communications.
Where CSC (corporate) sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 1 | 0.2% |
| Top 100,000 | 25 | 5.3% |
| Top 1,000,000 | 444 | 93.9% |
| Unranked | 3 | 0.6% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 192 | 40.6% | |
| .co.uk | 20 | 4.2% | |
| .net | 20 | 4.2% | |
| .fr | 15 | 3.2% | |
| .org | 12 | 2.5% | |
| .ca | 10 | 2.1% | |
| .de | 8 | 1.7% | |
| .com.au | 8 | 1.7% | |
| .com.br | 6 | 1.3% | |
| .es | 6 | 1.3% |
What CSC (corporate) users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 473 domains.
| Type | Service | Domains | Share of CSC (corporate) users |
|---|---|---|---|
| ESP | Amazon SES | 7 | 1.5% |
| ESP | Mimecast | 4 | 0.8% |
| ESP | Mailjet (Sinch) | 4 | 0.8% |
| ESP | SendGrid (Twilio) | 4 | 0.8% |
| ESP | Mailgun | 3 | 0.6% |
| ESP | Masiv | 3 | 0.6% |
| ESP | Proofpoint | 2 | 0.4% |
| ESP | Elastic Email | 2 | 0.4% |
| ESP | HubSpot | 2 | 0.4% |
| ESP | Marketo (Adobe) | 2 | 0.4% |
CSC in hybrid email stacks
Organisations using CSC for corporate email typically pair it with specialist transactional services such as SendGrid, requiring careful alignment of DKIM, SPF, and DMARC policies across both infrastructure layers. Email senders and administrators auditing these domains should expect multiple MX, DKIM, and sending-domain configurations, and should test policy alignment to avoid unintended rejections or failures when mail routes between CSC and third-party providers.
See the full CSC (corporate) data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Should I test email deliverability against CSC-hosted mailboxes?
Yes, if your audience includes small-and-medium-sized businesses, since CSC's customer base is concentrated in the long tail of the website landscape. Testing against CSC helps identify authentication and routing issues typical of the hybrid email architectures these organisations commonly run.
How many domains use CSC (corporate)?
473 domains in the Tranco top-1M use CSC (corporate) as their mailbox provider as of September 24, 2026 (0.07% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is CSC (corporate) common enough to affect email deliverability testing?
CSC (corporate) 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 CSC (corporate) most?
CSC (corporate)'s largest TLD is .com (40.6% of its domains); it appears across 100 TLDs in total.