Whitepaper uses Substack as their primary email service provider. Their email authentication setup is solid (score 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 Postmark DMARC. Policy
p=reject means receivers actively block or quarantine spoofed mail.
SPF alignment: observed emails use a third-party return-path (mg1.substack.com) — SPF passes there but doesn't align with whitepaper.substack.com, so DMARC has to rely on DKIM alignment.
DKIM alignment: observed emails sign with a third-party DKIM key (mg1.substack.com) — DKIM passes there but doesn't align with whitepaper.substack.com, so DMARC has to rely on SPF alignment.
TLS: 0% TLS 1.3, 100% TLS 1.2 (across 24 sends).
Delivery: fast — 89% of emails in the last 7 days arrive in under 10 seconds (across 9 sends).
Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).
None — only the primary ESP(s) shown aboveESPs 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.
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.
Probed: whitepaper.substack.com, mg1.substack.com
Folder distribution across all emails from this brand observed in Gmail inboxes. High inbox % = good deliverability; spam appearances are the headline signal.
| Folder | Count | Share |
|---|---|---|
| inbox | 25 | 100.0% |
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.
| ESP | Emails | Placement | Inbox % | Tabs % | Spam % |
|---|---|---|---|---|---|
| Substack | 25 | 100.0% | 0.0% | 0.0% |
Weekly observations per ESP. Brands often run multiple ESPs concurrently — marketing on one, transactional on another — so this chart shows usage rather than switches.
IP addresses whitepaper.substack.com has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 161.38.202.238 | mg-202-238.substack.com |
3 | 1 | Check → |
| 159.112.244.50 | v550.v5375b7fa.use4.send.mailgun.net |
3 | 1 | Check → |
| 159.112.244.60 | v560.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.135.230.34 | mg-230-34.substack.com |
2 | — | Check → |
| 161.38.195.132 | mg-195-132.substack.com |
2 | — | Check → |
| 161.38.197.240 | mg-197-240.substack.com |
2 | — | Check → |
| 161.38.202.234 | mg-202-234.substack.com |
2 | — | Check → |
| 159.135.235.32 | mg-235-32.substack.com |
2 | 1 | Check → |
| 159.112.244.62 | v562.v5375b7fa.use4.send.mailgun.net |
2 | 1 | Check → |
| 159.112.244.49 | v549.v5375b7fa.use4.send.mailgun.net |
2 | 2 | Check → |
| 159.112.244.37 | v537.v5375b7fa.use4.send.mailgun.net |
1 | — | Check → |
| 159.112.244.39 | v539.v5375b7fa.use4.send.mailgun.net |
1 | — | Check → |
| 159.112.244.64 | v564.v5375b7fa.use4.send.mailgun.net |
1 | — | Check → |
| 161.38.200.213 | mg-200-213.substack.com |
1 | 1 | Check → |
| 159.112.244.38 | v538.v5375b7fa.use4.send.mailgun.net |
1 | 1 | Check → |
| 161.38.202.34 | mg-202-34.substack.com |
1 | 1 | Check → |
| 159.112.244.63 | v563.v5375b7fa.use4.send.mailgun.net |
1 | 1 | Check → |
| 159.112.244.61 | v561.v5375b7fa.use4.send.mailgun.net |
1 | 1 | Check → |
| Domain | ESPs detected | Delivery (7d) |
|---|---|---|
whitepaper.substack.com | Substack 30 |