Www 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 (mg-d1.substack.com, mg-d0.substack.com, mg2.substack.com) — SPF passes there but doesn't align with www.substack.com, so DMARC has to rely on DKIM alignment.
DKIM alignment: observed emails sign with a third-party DKIM key (mg-d0.substack.com, mg-d1.substack.com, mg2.substack.com) — DKIM passes there but doesn't align with www.substack.com, so DMARC has to rely on SPF alignment.
TLS: 5% TLS 1.3, 95% TLS 1.2 (across 63 sends).
Delivery: fast — 80% of emails in the last 7 days arrive in under 10 seconds (across 20 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: www.substack.com, mg1.substack.com, mg-d1.substack.com, mg2.substack.com, mg-d0.substack.com, mg-tx1.substack.com, anglernook.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 | 97 | 95.1% |
| promotions | 5 | 4.9% |
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 | 102 | 95.1% | 4.9% | 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 www.substack.com has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 159.112.244.23 | v523.v5375b7fa.use4.send.mailgun.net |
10 | — | Check → |
| 159.112.244.8 | v58.v5375b7fa.use4.send.mailgun.net |
5 | — | Check → |
| 159.112.244.44 | v544.v5375b7fa.use4.send.mailgun.net |
4 | — | Check → |
| 159.112.244.59 | v559.v5375b7fa.use4.send.mailgun.net |
4 | 4 | Check → |
| 161.38.195.184 | mg-195-184.substack.com |
3 | — | Check → |
| 159.112.244.14 | v514.v5375b7fa.use4.send.mailgun.net |
3 | — | Check → |
| 161.38.201.184 | v5184.v5075e2e3.usw1.send.mailgun.net |
3 | 3 | Check → |
| 159.135.235.32 | mg-235-32.substack.com |
3 | 3 | Check → |
| 161.38.202.34 | mg-202-34.substack.com |
2 | — | Check → |
| 159.112.244.5 | v55.v5375b7fa.use4.send.mailgun.net |
2 | 1 | Check → |
| 159.112.244.35 | v535.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.112.244.55 | v555.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 161.38.200.213 | mg-200-213.substack.com |
2 | — | Check → |
| 159.112.244.20 | v520.v5375b7fa.use4.send.mailgun.net |
2 | 1 | Check → |
| 159.112.244.32 | v532.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.112.244.46 | v546.v5375b7fa.use4.send.mailgun.net |
2 | 1 | Check → |
| 69.72.47.244 | mg-47-244.substack.com |
2 | 1 | Check → |
| 159.112.244.28 | v528.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.112.244.26 | v526.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 143.55.229.170 | v5170.v56063cb6.use4.send.mailgun.net |
2 | — | Check → |
| 161.38.201.135 | v5135.v5075e2e3.usw1.send.mailgun.net |
2 | — | Check → |
| 159.112.244.66 | v566.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.135.230.34 | mg-230-34.substack.com |
2 | 1 | Check → |
| 159.112.244.53 | v553.v5375b7fa.use4.send.mailgun.net |
2 | — | Check → |
| 159.112.244.58 | v558.v5375b7fa.use4.send.mailgun.net |
2 | 1 | Check → |
| Domain | ESPs detected | Delivery (7d) |
|---|---|---|
www.substack.com | Substack 107 |