Mimecast mailbox provider
According to Live Direct Marketing's daily Tranco top-1M scan (September 12, 2026), Mimecast is the mailbox provider for 9,739 domains — 1.46% of 665,310 domains with MX records. Detection method: primary MX record (lowest preference).
Key facts
- 9,739 domains in the Tranco top-1M use Mimecast (1.46% of domains with MX records).
- Snapshot date: 2026-09-12 — recomputed every day.
- 30-day share change: -0.03 pp.
- Strongest TLD: .com (59.4% of its domains).
- Region skew: Global / US-skewed.
- Most co-used service: Mimecast.
- Directory category: email security gateway.
Why Mimecast appears in this category
UK/global cloud secure email gateway, very large enterprise share.
We classify it as a email security gateway 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.
Mimecast is an email security, archiving, and compliance platform that organisations use to protect, store, and manage email communications. It acts as a mail filter and cloud archive layer, sitting between senders and mailbox infrastructure to scan messages, enforce security policies, and maintain regulatory compliance.
Across the Tranco top-1 million domains, Mimecast sits predominantly in the long tail—used by mid-market and smaller organisations rather than the world's largest brands. Its footprint is concentrated in the .com space with a Global and US-skewed user base. For senders, this means Mimecast recipients represent a substantial but decentralised audience; for recipients, it signals that Mimecast's filtering and archiving decisions will affect what email they receive. Notably, Mimecast's market share has been declining, suggesting ongoing consolidation and migration within the email security sector.
Where Mimecast sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 19 | 0.2% |
| Top 10,000 | 125 | 1.3% |
| Top 100,000 | 1,343 | 13.8% |
| Top 1,000,000 | 8,208 | 84.3% |
| Unranked | 44 | 0.5% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 5,781 | 59.4% | |
| .org | 798 | 8.2% | |
| .co.uk | 614 | 6.3% | |
| .co.za | 337 | 3.5% | |
| .com.au | 297 | 3.0% | |
| .net | 178 | 1.8% | |
| .org.uk | 144 | 1.5% | |
| .de | 115 | 1.2% | |
| .fr | 104 | 1.1% | |
| .gov | 86 | 0.9% |
What Mimecast users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 9,739 domains.
| Type | Service | Domains | Share of Mimecast users |
|---|---|---|---|
| ESP | Mimecast | 7,004 | 71.9% |
| ESP | Salesforce | 1,133 | 11.6% |
| ESP | SendGrid (Twilio) | 1,003 | 10.3% |
| ESP | Amazon SES | 979 | 10.1% |
| ESP | HubSpot | 767 | 7.9% |
| ESP | Zendesk | 742 | 7.6% |
| ESP | Mailchimp | 651 | 6.7% |
| ESP | Mandrill | 622 | 6.4% |
| ESP | Mailgun | 513 | 5.3% |
| ESP | Marketo (Adobe) | 238 | 2.4% |
Mimecast's security scanning and email delivery
Mimecast's default posture is to scan inbound email for threats—malware, phishing, advanced attacks—and archive every message for compliance. This scanning layer can delay delivery slightly and occasionally reject or quarantine mail if it triggers a Mimecast security policy. Senders whose email is frequently caught in Mimecast's reputation or content filters may see delivery delays or rejections; conversely, mail with proper authentication (SPF, DKIM, DMARC) and clean sending infrastructure typically passes through without friction. Understanding Mimecast's filtering behaviour is less critical than it is for consumer-facing providers like Gmail, but becomes relevant when testing email to mid-market organisations or troubleshooting delivery within that segment.
See the full Mimecast data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Why should email senders care about Mimecast?
Mimecast filters and archives email for thousands of organisations globally; if your recipients use it, your deliverability depends partly on passing its security scanning and reputation checks. Testing against Mimecast is less universal than testing against Gmail or Outlook, but relevant if you send to mid-market organisations or need to troubleshoot delivery within that segment.
How many domains use Mimecast?
9,739 domains in the Tranco top-1M use Mimecast as their mailbox provider as of September 12, 2026 (1.46% of domains with MX records), according to Live Direct Marketing's daily DNS scan.
Is Mimecast common enough to affect email deliverability testing?
Mimecast accounts for 1.46% 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.
Is Mimecast growing or declining?
Mimecast is declining — its share moved -0.03 pp over the last 30 days (as of September 12, 2026).
Which countries or TLDs use Mimecast most?
Mimecast's largest TLD is .com (59.4% of its domains); it appears across 180 TLDs in total.