Cisco IronPort (ICPbounce) email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 16, 2026), Cisco IronPort (ICPbounce) is the email service provider (ESP) for 292 domains — 0.05% of 634,905 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 292 domains in the Tranco top-1M use Cisco IronPort (ICPbounce) (0.05% of SPF-publishing domains).
- Snapshot date: 2026-09-16 — recomputed every day.
- Strongest TLD: .com (64.0% of its domains).
- Most co-used service: Microsoft 365.
- Directory category: email security gateway.
Why Cisco IronPort (ICPbounce) appears in this category
Cisco IronPort — bounce-handling SPF domain.
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.
Cisco IronPort (marketed as ICPbounce) is an email delivery and security platform operated by Cisco Systems that enables organizations to send bulk email, manage sender reputation, and filter abuse across their outbound mail infrastructure.
IronPort's footprint skews towards smaller and mid-market sites rather than the largest brands, concentrated in .com registrations, and most often appears alongside Microsoft 365. For email professionals, this pattern signals that multi-sender orchestration—especially in Microsoft-integrated environments—is common, requiring careful SPF alignment and reputation monitoring across parallel sending channels.
Where Cisco IronPort (ICPbounce) sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 1 | 0.3% |
| Top 10,000 | 2 | 0.7% |
| Top 100,000 | 26 | 8.9% |
| Top 1,000,000 | 259 | 88.7% |
| Unranked | 4 | 1.4% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 187 | 64.0% | |
| .org | 53 | 18.2% | |
| .net | 10 | 3.4% | |
| .edu | 9 | 3.1% | |
| .co.uk | 6 | 2.1% | |
| .gov | 4 | 1.4% | |
| .ca | 4 | 1.4% | |
| .co.nz | 2 | 0.7% | |
| .nl | 1 | 0.3% | |
| .fm | 1 | 0.3% |
What Cisco IronPort (ICPbounce) users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 292 domains.
| Type | Service | Domains | Share of Cisco IronPort (ICPbounce) users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 107 | 36.6% |
| Mailbox | Google Workspace | 75 | 25.7% |
| Mailbox | Mimecast | 23 | 7.9% |
| Mailbox | Unknown / Other | 14 | 4.8% |
| Mailbox | Proofpoint | 14 | 4.8% |
| Mailbox | Self-Hosted | 12 | 4.1% |
| ESP | SendGrid (Twilio) | 38 | 13.0% |
| ESP | Amazon SES | 37 | 12.7% |
| ESP | HubSpot | 24 | 8.2% |
| ESP | Mailchimp | 21 | 7.2% |
IronPort as a Secondary Sending Channel in Multi-Sender Setups
When IronPort SPF includes appear on a domain—particularly those already using Microsoft 365—they typically indicate a secondary or specialized sending path rather than the primary outbound route. This split-sender architecture can introduce reputation fragmentation if the domains are not properly coordinated through authentication records (SPF, DKIM, DMARC), and monitoring both sending channels' bounce and complaint rates becomes essential for maintaining consistent deliverability.
See the full Cisco IronPort (ICPbounce) data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Why do I see Cisco IronPort in my domain's SPF record?
Your domain's SPF record includes a reference to Cisco IronPort's infrastructure if you use their email delivery service or a third-party application that sends mail on your behalf using IronPort. This is normal if IronPort is one of your authorized sending channels.
How many domains use Cisco IronPort (ICPbounce)?
292 domains in the Tranco top-1M use Cisco IronPort (ICPbounce) as their email service provider (ESP) as of September 16, 2026 (0.05% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Cisco IronPort (ICPbounce) common enough to affect email deliverability testing?
Cisco IronPort (ICPbounce) accounts for 0.05% 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 Cisco IronPort (ICPbounce) most?
Cisco IronPort (ICPbounce)'s largest TLD is .com (64.0% of its domains); it appears across 25 TLDs in total.