According to Live Direct Marketing's daily Tranco top-1M scan (July 12, 2026), IS.CC Relay is the email service provider (ESP) for 98 domains — 0.02% of 617,244 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
IS.CC Relay is an email relay service that appears in the SPF records of websites, configured via include: mechanisms to authorise mail delivery. It functions as an infrastructure component for organisations sending mail through a relay rather than directly from their own mail servers.
IS.CC Relay's footprint is concentrated in the long tail of smaller websites and self-hosted deployments, predominantly in the .com space, rather than amongst mainstream enterprises. This distribution indicates that the relay serves organisations seeking lightweight email infrastructure alongside self-managed mail systems, rather than centralised platform solutions.
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 0 | 0.0% |
| Top 10,000 | 0 | 0.0% |
| Top 100,000 | 2 | 2.0% |
| Top 1,000,000 | 78 | 79.6% |
| Unranked | 18 | 18.4% |
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 56 | 57.1% | |
| .net | 7 | 7.1% | |
| .org | 7 | 7.1% | |
| .cl | 3 | 3.1% | |
| .in | 2 | 2.0% | |
| .info | 2 | 2.0% | |
| .com.bd | 2 | 2.0% | |
| .ee | 1 | 1.0% | |
| .ir | 1 | 1.0% | |
| .gh | 1 | 1.0% |
Cross-tabulated from the same daily snapshot — the other email services seen on the same 98 domains.
| Type | Service | Domains | Share of IS.CC Relay users |
|---|---|---|---|
| Mailbox | Self-Hosted | 81 | 82.7% |
| Mailbox | Google Workspace | 8 | 8.2% |
| Mailbox | Unknown / Other | 3 | 3.1% |
| Mailbox | Microsoft 365 | 2 | 2.0% |
| Mailbox | Generic / unmatched (mx*.*) | 1 | 1.0% |
| Mailbox | Barracuda | 1 | 1.0% |
| ESP | MailChannels | 23 | 23.5% |
| ESP | Amazon SES | 3 | 3.1% |
| ESP | Mailgun | 2 | 2.0% |
| ESP | Mailchimp | 1 | 1.0% |
When a sending domain routes mail through IS.CC Relay via SPF, the domain's inbox placement depends on both its own sender reputation and the relay's operational practices. If IS.CC Relay is misconfigured—for example, with poor SPF/DKIM alignment or weak authentication hygiene—it can degrade mail deliverability for all domains using it, regardless of their individual sender behaviour. Organisations deploying IS.CC Relay must ensure the relay maintains proper authentication configuration and operational standards, as its reputation becomes a shared dependency in the mail path.
See the full IS.CC Relay data page (KPI cards, trend, sample domains) →
Your mail's inbox placement depends on both your domain's sender authentication records and IS.CC Relay's configuration and reputation; if the relay is misconfigured or has poor operational standing, it may degrade deliverability for your domain even if your own sender reputation is clean.
98 domains in the Tranco top-1M use IS.CC Relay as their email service provider (ESP) as of July 12, 2026 (0.02% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
IS.CC Relay accounts for 0.02% of SPF-publishing domains 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.CC Relay's largest TLD is .com (57.1% of its domains); it appears across 26 TLDs in total.