Flowmailer email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 20, 2026), Flowmailer is the email service provider (ESP) for 749 domains — 0.12% of 638,158 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 749 domains in the Tranco top-1M use Flowmailer (0.12% of SPF-publishing domains).
- Snapshot date: 2026-09-20 — recomputed every day.
- Strongest TLD: .nl (46.3% of its domains).
- Most co-used service: Microsoft 365.
- Directory category: email service provider.
Why Flowmailer appears in this category
Dutch transactional email platform, B2B-leaning.
We classify it as a email service provider 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.
Flowmailer is a Dutch email service provider that manages transactional and marketing mail delivery for its customers. Operated from the Netherlands, it serves organisations across Northern Europe with a focus on regional data residency and compliance.
In global mail infrastructure, Flowmailer appears as an SPF include on smaller and mid-market websites rather than major enterprise brands, with notable concentration in the .nl domain space. It frequently co-occurs with Microsoft 365 in organisations that deploy segmented mail handling, where Flowmailer manages specific mail flows whilst a primary platform handles general corporate traffic. This pattern reflects its role as a supplementary provider rather than a primary platform.
Where Flowmailer sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 2 | 0.3% |
| Top 10,000 | 9 | 1.2% |
| Top 100,000 | 87 | 11.6% |
| Top 1,000,000 | 646 | 86.2% |
| Unranked | 5 | 0.7% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .nl | 347 | 46.3% | |
| .com | 161 | 21.5% | |
| .de | 45 | 6.0% | |
| .se | 42 | 5.6% | |
| .be | 39 | 5.2% | |
| .no | 23 | 3.1% | |
| .net | 13 | 1.7% | |
| .io | 9 | 1.2% | |
| .eu | 9 | 1.2% | |
| .co.uk | 9 | 1.2% |
What Flowmailer users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 749 domains.
| Type | Service | Domains | Share of Flowmailer users |
|---|---|---|---|
| Mailbox | Microsoft 365 | 473 | 63.2% |
| Mailbox | Google Workspace | 117 | 15.6% |
| Mailbox | Self-Hosted | 30 | 4.0% |
| Mailbox | Unknown / Other | 22 | 2.9% |
| Mailbox | Generic / unmatched (mx*.*) | 16 | 2.1% |
| Mailbox | Barracuda | 15 | 2.0% |
| ESP | Mandrill | 95 | 12.7% |
| ESP | SendGrid (Twilio) | 95 | 12.7% |
| ESP | Zendesk | 79 | 10.5% |
| ESP | Mailjet (Sinch) | 73 | 9.7% |
Flowmailer in Microsoft 365 hybrid configurations
Organisations that combine Flowmailer with Microsoft 365 typically isolate transactional, compliance-critical, or high-volume mail on Flowmailer's region-hosted infrastructure whilst routing general corporate mail through their primary platform. This segmentation appeals to European entities where data residency, audit trail isolation, or mail load balancing justifies multiple outbound providers. When both providers appear in an organisation's SPF record, each must authenticate correctly for delivery to succeed, and mail routing must be properly configured to match SPF claims.
See the full Flowmailer data page (KPI cards, trend, sample domains) →
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Frequently asked questions
Do I need to test or whitelist Flowmailer for email deliverability?
Only if your organisation sends mail via Flowmailer—verify your outbound mail routing and SPF configuration. If Flowmailer appears in inbound mail you receive, the sender is responsible for configuring it correctly.
How many domains use Flowmailer?
749 domains in the Tranco top-1M use Flowmailer as their email service provider (ESP) as of September 20, 2026 (0.12% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Flowmailer common enough to affect email deliverability testing?
Flowmailer accounts for 0.12% 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 Flowmailer most?
Flowmailer's largest TLD is .nl (46.3% of its domains); it appears across 34 TLDs in total.