Email Detective — ESP Tracker

Postmarkapp

postmarkapp.com ↗

🏆Rank #23,480 🏷 SaaS 🇺🇸United States ✓ Inbox 100%

Postmarkapp uses ActiveCampaign for marketing email and Postmark for transactional/notifications. They rank #23,480 in the Tranco list of most-popular domains. Email goes out from 3 different subdomains. Their email authentication setup is solid (score 85/100). We've recorded 1 ESP change since first observing this brand.

Marketing ESPActiveCampaign

Transactional ESPPostmark

Total observations86

Active days23

Avg per active day3.7

Last activity📬 Active · 8 days ago

Cadence~every 3 days

Other technologies

Non-ESP tools detected in this brand's emails. Independent of who sends — a brand can use any combination.

HTML builder

Stripo

Email setup 85/100

Authentication signals observed in this brand's emails. SPF, DKIM and DMARC are the standard sender-authentication stack — see the DMARC policy below for whether spoofing is actually blocked or just monitored. One-click unsubscribe meets Google & Yahoo's bulk-sender requirements.

SPF / DKIM / DMARC above reflect the last 10 emails we've observed. DMARC policy is read live from DNS.

DMARC reports sent to DMARC Digests. Policy p=reject means receivers actively block or quarantine spoofed mail.

SPF alignment: 84% of observed emails use an aligned return-path (pmbounces.postmarkapp.com, ac-bounces.fyi.postmarkapp.com, ac-bounces.postmarkapp.com); the rest use third-party paths (capitani.marketing, themathergroupllc.com, pm-bounces.schippers.eu) where DMARC has to rely on DKIM alignment.

DKIM alignment: all 40 observed emails sign with a domain aligned with postmarkapp.com (postmarkapp.com, fyi.postmarkapp.com). DKIM authenticates the visible From — supports DMARC directly.

TLS: modern — 100% TLS 1.3 (across 24 sends).

Other ESPs detected

Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).

Confirmed senders

ESPs we've seen sending email for this brand. Green = confirmed by SPF, sender IP rDNS, or known infra pairing (label shows the source). Grey = observed but not yet confirmed by SPF or PTR.

ActiveCampaign ✓ confirmed Postmark ✓ confirmed

Other SPF authorizations

ESPs this brand has authorized in their SPF record. We confirm them with a green ✓ only after seeing recurring use (3+ emails across 2+ days). Until then they stay here — either we haven't observed any email yet, or we've seen a handful but not enough to call them a regular sender for the brand.

Campaign Monitor Google Workspace

Probed: postmarkapp.com, pmbounces.postmarkapp.com, pm-bounces.schippers.eu, themathergroupllc.com, capitani.marketing, ac-bounces.fyi.postmarkapp.com, ac-bounces.postmarkapp.com, fyi.postmarkapp.com, mtasv.net

Where emails landed (Gmail)

Folder distribution across all emails from this brand observed in Gmail inboxes. High inbox % = good deliverability; spam appearances are the headline signal.

Placement by ESP

Which ESP's emails are landing where. Sorted by spam % so problem senders surface first. Brands using one ESP for marketing and another for transactional often see very different placement profiles per ESP. Per-ESP folder data only started being captured recently — counts here may be smaller than the total above until backfill catches up.

Daily observations per ESP. Brands often run multiple ESPs concurrently — marketing on one, transactional on another — so this chart shows usage rather than switches.

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Sending IPs

IP addresses postmarkapp.com has been observed sending from, and where their mail landed in Gmail.

Sending domains