According to Live Direct Marketing's daily Tranco top-1M scan (July 13, 2026), CSC (corporate) is the mailbox provider for 1,023 domains — 0.16% of 658,711 domains with MX records. Detection method: primary MX record (lowest preference).
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.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 0 | 0.0% |
| Top 100,000 | 30 | 2.9% |
| Top 1,000,000 | 733 | 71.7% |
| Unranked | 260 | 25.4% |
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 369 | 36.1% | |
| .net | 110 | 10.8% | |
| .fr | 47 | 4.6% | |
| .co.uk | 31 | 3.0% | |
| .tr | 25 | 2.4% | |
| .com.tr | 21 | 2.1% | |
| .biz | 18 | 1.8% | |
| .info | 17 | 1.7% | |
| .de | 16 | 1.6% | |
| .es | 16 | 1.6% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 1,023 domains.
| Type | Service | Domains | Share of CSC (corporate) users |
|---|---|---|---|
| ESP | Amazon SES | 5 | 0.5% |
| ESP | SendGrid (Twilio) | 5 | 0.5% |
| ESP | Mimecast | 4 | 0.4% |
| ESP | Masiv | 4 | 0.4% |
| ESP | Mailjet (Sinch) | 4 | 0.4% |
| ESP | Marketo (Adobe) | 2 | 0.2% |
| ESP | Elastic Email | 2 | 0.2% |
| ESP | Mandrill | 2 | 0.2% |
| ESP | Proofpoint | 2 | 0.2% |
| ESP | Mailgun | 2 | 0.2% |
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) →
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.
1,023 domains in the Tranco top-1M use CSC (corporate) as their mailbox provider as of July 13, 2026 (0.16% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
CSC (corporate) accounts for 0.16% 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.
CSC (corporate)'s largest TLD is .com (36.1% of its domains); it appears across 116 TLDs in total.