Customer uses Customer.io for marketing email and SendGrid for transactional/notifications. They rank #2,290 in the Tranco list of most-popular domains. We've also observed sends via 6 other providers: Salesforce CRM, Amazon SES, HubSpot, Intercom, Marketo, Mailgun. Email goes out from 2 different subdomains. Their email authentication setup is good (score 80/100). We've recorded 13 ESP changes since first observing this brand.
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=quarantine means receivers actively block or quarantine spoofed mail.
SPF alignment: all 1236 observed emails use a return-path aligned with customer.io (em614.customer.io, cio1.customer.io, bounces.customer.io). SPF authenticates the visible From — supports DMARC directly.
DKIM alignment: all 1206 observed emails sign with a domain aligned with customer.io (customer.io, cio1.customer.io, tests.customer.io). DKIM authenticates the visible From — supports DMARC directly.
TLS: 71% TLS 1.3, 29% TLS 1.2 (across 510 sends).
Delivery: fast — 92% of emails in the last 7 days arrive in under 10 seconds (across 202 sends).
Brands often use multiple ESPs (e.g. one for marketing, another for transactional/notifications).
Salesforce CRM 123 Zendesk 26 Amazon SES 9 HubSpot 2 Intercom 1 Marketo 1 Mailgun 1ESPs 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: customer.io, em1933.customer.io, bounces.customer.io, cio1.customer.io, em614.customer.io, tests.customer.io, cio1.login.customer.io, em908.customer.io, login.customer.io
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 | 1,143 | 99.0% |
| promotions | 12 | 1.0% |
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 % |
|---|---|---|---|---|---|
| Amazon SES | 5 | 100.0% | 0.0% | 0.0% | |
| Customer.io | 450 | 97.3% | 2.7% | 0.0% | |
| HubSpot | 2 | 100.0% | 0.0% | 0.0% | |
| Intercom | 1 | 100.0% | 0.0% | 0.0% | |
| Mailgun | 1 | 100.0% | 0.0% | 0.0% | |
| Marketo | 1 | 100.0% | 0.0% | 0.0% | |
| Salesforce CRM | 100 | 100.0% | 0.0% | 0.0% | |
| SendGrid | 387 | 100.0% | 0.0% | 0.0% | |
| Zendesk | 25 | 100.0% | 0.0% | 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 customer.io has been observed sending from, and where their mail landed in Gmail.
| IP | Hostname | Obs | Placement | Reputation |
|---|---|---|---|---|
| 159.183.125.42 | wfbttdnx.outbound-mail.sendgrid.net |
745 | 68 | Check → |
| 216.226.72.0 | m216226-72-0.proxy.laneful.net |
167 | 10 | Check → |
| 161.38.192.92 | v592.v56682d52.use4.send.mailgun.net |
77 | 10 | Check → |
| 143.55.227.49 | v549.v54f91261.use4.send.mailgun.net |
74 | 13 | Check → |
| 69.72.44.3 | v53.v5e5d4d68.usw1.send.mailgun.net |
67 | 3 | Check → |
| 161.38.196.8 | v58.v5ab752a9.usw1.send.mailgun.net |
66 | 12 | Check → |
| 161.38.192.97 | v597.v56682d52.use4.send.mailgun.net |
65 | 8 | Check → |
| 69.72.44.4 | v54.v5e5d4d68.usw1.send.mailgun.net |
65 | 11 | Check → |
| 198.37.145.102 | o1.mailer.workramp.com |
56 | 3 | Check → |
| 161.38.196.35 | v535.v5ab752a9.usw1.send.mailgun.net |
42 | 8 | Check → |
| 192.161.149.40 | mta-out10.pod23.use1.zdsys.com |
5 | — | Check → |
| 192.161.149.31 | mta-out1.pod23.use1.zdsys.com |
4 | 1 | Check → |
| 192.161.149.43 | mta-out13.pod23.use1.zdsys.com |
2 | — | Check → |
| 192.161.149.42 | mta-out12.pod23.use1.zdsys.com |
2 | 1 | Check → |
| 192.161.149.38 | mta-out8.pod23.use1.zdsys.com |
2 | — | Check → |
| 192.161.149.35 | mta-out5.pod23.use1.zdsys.com |
2 | — | Check → |
| 192.161.149.36 | mta-out6.pod23.use1.zdsys.com |
2 | 2 | Check → |
| 192.161.149.45 | mta-out15.pod23.use1.zdsys.com |
2 | 2 | Check → |
| 192.161.149.32 | mta-out2.pod23.use1.zdsys.com |
1 | — | Check → |
| 192.161.149.39 | mta-out9.pod23.use1.zdsys.com |
1 | — | Check → |
| 192.161.149.34 | mta-out4.pod23.use1.zdsys.com |
1 | — | Check → |
| 192.161.149.41 | mta-out11.pod23.use1.zdsys.com |
1 | — | Check → |
| Domain | ESPs detected | Delivery (7d) |
|---|---|---|
customer.io | SendGrid 804 Customer.io 627 Salesforce CRM 123 Zendesk 26 Amazon SES 9 HubSpot 2 Intercom 1 Marketo 1 Mailgun 1 | |
login.customer.io | Customer.io 14 |
