Blurb uses Sailthru as their primary email service provider. They rank #9,125 in the Tranco list of most-popular domains. Their email authentication setup is good (score 73/100). Missing: DMARC enforcement.
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.
DMARC reports sent to DMARC Digests. Policy
p=none is monitor-only — receivers won't act on spoofing yet.
SPF alignment: observed emails use a third-party return-path (mx.sailthru.com) — SPF passes there but doesn't align with blurb.com, so DMARC has to rely on DKIM alignment.
DKIM alignment: all 11 observed emails sign with a domain aligned with blurb.com (makebooks.blurb.com). DKIM authenticates the visible From — supports DMARC directly.
TLS: modern — 100% TLS 1.3 (across 5 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: blurb.com, mx.sailthru.com, makebooks.blurb.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 | 1 | 25.0% |
| promotions | 3 | 75.0% |
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 % |
|---|---|---|---|---|---|
| Sailthru | 4 | 25.0% | 75.0% | 0.0% |
Daily 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 blurb.com has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Reputation |
|---|---|---|---|
| 192.64.237.250 | pmta237-250.sailthru.com |
5 | Check → |
| 192.64.238.39 | mta238-39.sailthru.com |
5 | Check → |
| 192.64.237.180 | mta237-180.sailthru.com |
1 | Check → |
Per-IP inbox / promotions / spam is being collected and will appear here as new emails are observed.
| Domain | ESPs detected | Delivery (7d) |
|---|---|---|
makebooks.blurb.com | Sailthru 11 |
