Postmark email service provider (ESP)
According to Live Direct Marketing's daily Tranco top-1M scan (September 11, 2026), Postmark is the email service provider (ESP) for 2,935 domains — 0.47% of 631,089 SPF-publishing domains. Detection method: include: mechanisms in the SPF record.
Key facts
- 2,935 domains in the Tranco top-1M use Postmark (0.47% of SPF-publishing domains).
- Snapshot date: 2026-09-11 — recomputed every day.
- 30-day share change: +0.01 pp.
- Strongest TLD: .com (57.0% of its domains).
- Most co-used service: Google Workspace.
- Directory category: email service provider.
Why Postmark appears in this category
Transactional email service known for high deliverability and developer UX.
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.
Postmark is a transactional and bulk email delivery service operated by Wildbit, designed to help developers and applications send messages reliably through delegated SMTP infrastructure and managed sender authentication.
Postmark's footprint across the Tranco top-1 million is concentrated among smaller and mid-market .com sites, particularly those also using Google Workspace. For senders, this means joining a long-tail pool of customers whose sending behaviour collectively influences shared IP reputation; for receivers, Postmark's presence signals the likely scale and type of the sending organisation.
Where Postmark sits in the Tranco ranking
| Tranco rank band | Domains | Share of its base |
|---|---|---|
| Top 1,000 | 3 | 0.1% |
| Top 10,000 | 53 | 1.8% |
| Top 100,000 | 417 | 14.2% |
| Top 1,000,000 | 2,447 | 83.4% |
| Unranked | 15 | 0.5% |
Top-level domain split
| TLD | Domains | Share | |
|---|---|---|---|
| .com | 1,674 | 57.0% | |
| .org | 151 | 5.1% | |
| .io | 89 | 3.0% | |
| .net | 80 | 2.7% | |
| .co.uk | 74 | 2.5% | |
| .nl | 61 | 2.1% | |
| .de | 55 | 1.9% | |
| .co | 48 | 1.6% | |
| .com.au | 44 | 1.5% | |
| .fi | 35 | 1.2% |
What Postmark users also use
Cross-tabulated from the same daily snapshot — the other email services seen on the same 2,935 domains.
| Type | Service | Domains | Share of Postmark users |
|---|---|---|---|
| Mailbox | Google Workspace | 1,482 | 50.5% |
| Mailbox | Microsoft 365 | 635 | 21.6% |
| Mailbox | Self-Hosted | 143 | 4.9% |
| Mailbox | Generic / unmatched (mx*.*) | 109 | 3.7% |
| Mailbox | Unknown / Other | 84 | 2.9% |
| Mailbox | Mimecast | 65 | 2.2% |
| ESP | Mailchimp | 409 | 13.9% |
| ESP | Zendesk | 388 | 13.2% |
| ESP | SendGrid (Twilio) | 382 | 13.0% |
| ESP | Amazon SES | 374 | 12.7% |
SPF delegation and shared reputation pools
When a sender includes Postmark's SPF record via include:postmarkapp.com, the domain authorises Postmark's infrastructure to send mail on its behalf. This delegation means sender reputation is partly distributed: your emails benefit from Postmark's network standing, but can also be affected by the sending practices of other Postmark customers sharing the same IP space. Understanding this trade-off is essential when evaluating whether to route mail through a third-party provider.
See the full Postmark 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
Should I add Postmark to my domain's SPF record?
Add Postmark's SPF include only if you actively route mail through Postmark; if you do not, the include weakens your SPF record and creates security ambiguity. If you do use Postmark, add its <code>include:postmarkapp.com</code> mechanism to your SPF record, ensuring the total count of DNS lookups stays under ten.
How many domains use Postmark?
2,935 domains in the Tranco top-1M use Postmark as their email service provider (ESP) as of September 11, 2026 (0.47% of SPF-publishing domains), according to Live Direct Marketing's daily DNS scan.
Is Postmark common enough to affect email deliverability testing?
Postmark accounts for 0.47% 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 Postmark growing or declining?
Postmark has been stable — its share moved +0.01 pp over the last 30 days (as of September 11, 2026).
Which countries or TLDs use Postmark most?
Postmark's largest TLD is .com (57.0% of its domains); it appears across 152 TLDs in total.