IS.CC Relay email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 24, 2026), IS.CC Relay is the email service provider (ESP) for 96 domains — 0.02% of 637,420 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 96 domains in the Tranco top-1M use IS.CC Relay (0.02% of SPF-publishing domains).
- Snapshot date: 2026-09-24 — recomputed every day.
- Strongest TLD: .com (57.3% of its domains).
- Most co-used service: Self-Hosted.
- Directory category: email security gateway.
Why IS.CC Relay appears in this category
IS.CC — generic SMTP relay service.
We classify it as a email security gateway from include: mechanisms in the SPF record matching a maintained provider rule. This is infrastructure attribution from public DNS, not evidence of a direct contract or exclusive use.
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.
Where IS.CC Relay 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 | 2 | 2.1% |
| Top 1,000,000 | 93 | 96.9% |
| Unranked | 1 | 1.0% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 55 | 57.3% | |
| .org | 9 | 9.4% | |
| .net | 9 | 9.4% | |
| .cl | 4 | 4.2% | |
| .info | 2 | 2.1% | |
| .com.bd | 1 | 1.0% | |
| .ai | 1 | 1.0% | |
| .lv | 1 | 1.0% | |
| .website | 1 | 1.0% | |
| .ir | 1 | 1.0% |
What IS.CC Relay users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 96 domains.
| Type | Service | Domains | Share of IS.CC Relay users |
|---|---|---|---|
| Mailbox | Self-Hosted | 81 | 84.4% |
| Mailbox | Google Workspace | 7 | 7.3% |
| Mailbox | Generic / unmatched (mx*.*) | 2 | 2.1% |
| Mailbox | Unknown / Other | 2 | 2.1% |
| Mailbox | Microsoft 365 | 2 | 2.1% |
| Mailbox | Zoho Mail | 1 | 1.0% |
| ESP | MailChannels | 24 | 25.0% |
| ESP | Amazon SES | 3 | 3.1% |
| ESP | Constant Contact | 1 | 1.0% |
| ESP | Barracuda Essentials | 1 | 1.0% |
Relay configuration and sender reputation separation
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) →
Run a free inbox-placement test across Gmail, Outlook, Yahoo and more — see exactly where your mail lands and why.
Frequently asked questions
How does using IS.CC Relay affect whether my email reaches the inbox?
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.
How many domains use IS.CC Relay?
96 domains in the Tranco top-1M use IS.CC Relay as their email service provider (ESP) as of September 24, 2026 (0.02% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is IS.CC Relay common enough to affect email deliverability testing?
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.
Which countries or TLDs use IS.CC Relay most?
IS.CC Relay's largest TLD is .com (57.3% of its domains); it appears across 22 TLDs in total.