Automated messaging for tech companies.
Customer.io is the 11th most popular marketing ESP we track.
Detected by 322 distinct extension users.
Distribution of brands using Customer.io by industry. Helps you gauge whether this ESP is popular with businesses similar to yours. Brands tagged in two industries are counted in both.
Based on 239 of 252 brands tagged (95% coverage). Industries assigned automatically using AI; not every brand is tagged yet.
Where this ESP's emails land in Gmail. Each brand counted once (average of per-brand percentages) so a single high-volume sender can't dominate. Spam placement is mostly driven by the sender (list quality, content, complaint rate). This number reflects both the ESP's infrastructure AND the kind of senders who choose it — not just deliverability quality.
By volume: inbox 4,822 · promotions 332 · spam 14 (5,168 emails observed)
Percentages are averaged per brand (each counted once) across 119 brands using Customer.io with at least 5 placement observations each.
Underlying transactional infrastructure Customer.io routes through, detected from the sender hostname (PTR record) on each email's Received header. Bigger sample → more accurate.
Amazon SES
2 of 252 brands
204 as their primary ESP, the rest send transactional or secondary email through it. Primary users are listed first, then secondary.
| Brand | Role | Obs | Spam | Last seen |
|---|---|---|---|---|
|
Mixpanel
mixpanel.com
|
primary | 39 | 0.0% | 2026-06-25 |
|
Notion
notion.so
|
primary | 42 | 0.0% | 2026-06-28 |
|
Posthog
posthog.com
|
primary | 12 | 0.0% | 2026-06-24 |
|
Polymarket
polymarket.com
|
primary | 9 | 0.0% | 2026-06-25 |
|
Quillbot
quillbot.com
|
primary | 4 | 0.0% | 2026-06-24 |
|
Buffer
buffer.com
|
primary | 7 | 0.0% | 2026-06-29 |
|
Cursor
cursor.com
|
primary | 13 | 0.0% | 2026-06-29 |
|
Lovable
lovable.dev
|
primary | 72 | 0.0% | 2026-06-30 |
|
Railway
railway.app
|
primary | 16 | 0.0% | 2026-06-29 |
|
Immowelt
immowelt.de
|
primary | 1 | — | 2026-05-18 |
|
Make
make.com
|
primary | 28 | 0.0% | 2026-06-30 |
|
Use
use.ai
|
primary | 6 | 0.0% | 2026-06-16 |
|
Angi
angi.com
|
primary | 5 | 0.0% | 2026-05-21 |
|
Neon
neon.tech
|
primary | 10 | 0.0% | 2026-06-26 |
|
N8n
n8n.io
|
primary | 33 | 0.0% | 2026-06-24 |
|
Gitbook
gitbook.com
|
primary | 6 | 0.0% | 2026-06-26 |
|
Apollo
apollo.io
|
primary | 81 | 1.2% | 2026-06-26 |
|
Higgsfield
higgsfield.ai
|
primary | 6 | 0.0% | 2026-06-23 |
|
Openrouter
openrouter.ai
|
primary | 6 | 0.0% | 2026-06-17 |
|
Ifttt
ifttt.com
|
primary | 4 | 0.0% | 2026-06-24 |
|
Weglot
weglot.com
|
primary | 1 | — | 2026-06-16 |
|
Gtmetrix
gtmetrix.com
|
primary | 1 | — | 2026-05-06 |
|
Tryfi
tryfi.com
|
primary | 1 | — | 2026-06-15 |
|
Vidiq
vidiq.com
|
primary | 17 | 0.0% | 2026-06-25 |
|
Scribehow
scribehow.com
|
primary | 7 | 0.0% | 2026-06-18 |
|
Kalshi
kalshi.com
|
primary | 6 | 0.0% | 2026-06-25 |
|
Cloudways
cloudways.com
|
primary | 22 | 0.0% | 2026-06-24 |
|
Heygen
heygen.com
|
primary | 30 | 0.0% | 2026-06-22 |
|
Emcd
emcd.io
|
primary | 1 | — | 2026-05-07 |
|
Superwall
superwall.com
|
primary | 1 | — | 2026-05-05 |
|
23andme
23andme.com
|
primary | 4 | 0.0% | 2026-06-09 |
|
Lemonade
lemonade.com
|
primary | 2 | — | 2026-06-26 |
|
Docsity
docsity.com
|
primary | 1 | — | 2026-05-14 |
|
Optisigns
optisigns.com
|
primary | 3 | 0.0% | 2026-06-25 |
|
Wisestamp
wisestamp.com
|
primary | 5 | 0.0% | 2026-06-15 |
|
Rescuetime
rescuetime.com
|
primary | 1 | — | 2026-06-18 |
|
Stonly
stonly.com
|
primary | 4 | 0.0% | 2026-06-11 |
|
Pitch
pitch.com
|
primary | 1 | — | 2026-04-28 |
|
Realpython
realpython.com
|
primary | 1 | — | 2026-06-14 |
|
Rebrandly
rebrandly.com
|
primary | 32 | 0.0% | 2026-06-30 |
|
Prezly
prezly.com
|
primary | 1 | — | 2026-05-13 |
|
Hunter
hunter.io
|
primary | 27 | 3.7% | 2026-06-30 |
|
Weworkremotely
weworkremotely.com
|
primary | 1 | — | 2026-06-15 |
|
Riverside
riverside.fm
|
primary | 9 | 0.0% | 2026-06-30 |
|
Pdfguru
pdfguru.com
|
primary | 3 | 0.0% | 2026-06-22 |
|
Wyzant
wyzant.com
|
primary | 1 | — | 2026-06-26 |
|
Theliven
theliven.com
|
primary | 17 | 0.0% | 2026-05-15 |
|
Novu
novu.co
|
primary | 1 | — | 2026-05-05 |
|
Hint
hint.app
|
primary | 1 | — | 2026-05-25 |
|
Daily
daily.dev
|
primary | 4 | 0.0% | 2026-06-24 |
|
Madmuscles
madmuscles.com
|
primary | 5 | 0.0% | 2026-06-23 |
|
Uphold
uphold.com
|
primary | 1 | — | 2026-06-19 |
|
Kittl
kittl.com
|
primary | 2 | — | 2026-06-22 |
|
Omr
omr.com
|
primary | 19 | 0.0% | 2026-06-22 |
|
Georgiaaquarium
georgiaaquarium.org
|
primary | 3 | 0.0% | 2026-06-23 |
|
Cxl
cxl.com
|
primary | 8 | 0.0% | 2026-06-09 |
|
Thebestpdf
thebestpdf.com
|
primary | 2 | — | 2026-06-17 |
|
Lemlist
lemlist.com
|
primary | 7 | 0.0% | 2026-06-26 |
|
Puck
puck.news
|
primary | 1 | — | 2026-05-15 |
|
Pdfleader
pdfleader.com
|
primary | 2 | — | 2026-06-16 |
|
Tldv
tldv.io
|
primary | 26 | 0.0% | 2026-06-29 |
|
Default
default.com
|
primary | 1 | — | 2026-05-27 |
|
Doublegood
doublegood.com
|
primary | 3 | 0.0% | 2026-06-29 |
|
Pagaleve
pagaleve.com.br
|
primary | 1 | — | 2026-06-30 |
|
Gostudent
gostudent.org
|
primary | 1 | — | 2026-06-01 |
|
Senja
senja.io
|
primary | 32 | 0.0% | 2026-06-29 |
|
Zendocs
zendocs.com
|
primary | 1 | — | 2026-05-11 |
|
Scoreapp
scoreapp.com
|
primary | 22 | 0.0% | 2026-06-24 |
|
Sudowrite
sudowrite.com
|
primary | 1 | — | 2026-05-23 |
|
Thirdbridge
thirdbridge.com
|
primary | 1 | — | 2026-06-01 |
|
Attio
attio.com
|
primary | 26 | 0.0% | 2026-06-30 |
|
Xoxoday
xoxoday.com
|
primary | 2 | — | 2026-06-04 |
|
Gelato
gelato.com
|
primary | 2 | — | 2026-05-13 |
|
Mybillie
mybillie.com
|
primary | 1 | — | 2026-05-06 |
|
Contra
contra.com
|
primary | 5 | 0.0% | 2026-06-10 |
|
Zight
zight.com
|
primary | 12 | 0.0% | 2026-06-23 |
|
Bookretreats
bookretreats.com
|
primary | 2 | — | 2026-06-21 |
|
Firecrawl
firecrawl.dev
|
primary | 4 | 0.0% | 2026-06-28 |
|
Jitter
jitter.video
|
primary | 2 | — | 2026-06-17 |
|
Beefree
beefree.io
|
primary | 33 | 0.0% | 2026-06-22 |
|
Kapa
kapa.ai
|
primary | 2 | — | 2026-06-12 |
|
Aferry
aferry.com
|
primary | 1 | — | 2026-05-26 |
|
Mobbin
mobbin.com
|
primary | 3 | 0.0% | 2026-05-27 |
|
Air
air.inc
|
primary | 3 | 0.0% | 2026-06-24 |
|
Wallstreetzen
wallstreetzen.com
|
primary | 34 | 0.0% | 2026-06-18 |
|
Gumlet
gumlet.com
|
primary | 1 | — | 2026-05-20 |
|
Maven
maven.com
|
primary | 25 | 0.0% | 2026-06-30 |
|
Alan
alan.com
|
primary | 1 | — | 2026-05-26 |
|
Sunsama
sunsama.com
|
primary | 3 | 0.0% | 2026-05-27 |
|
Brizy
brizy.io
|
primary | 1 | — | 2026-06-08 |
|
Warmy
warmy.io
|
primary | 53 | 0.0% | 2026-06-30 |
|
Airops
airops.com
|
primary | 3 | 0.0% | 2026-05-18 |
|
Dust
dust.tt
|
primary | 1 | — | 2026-05-22 |
|
Rightcapital
rightcapital.com
|
primary | 1 | — | 2026-06-25 |
|
Getquin
getquin.com
|
primary | 12 | 0.0% | 2026-06-22 |
|
Signitic
signitic.com
|
primary | 13 | 0.0% | 2026-06-26 |
|
Klar
klar.mx
|
primary | 1 | — | 2026-06-15 |
|
Fyxer
fyxer.com
|
primary | 27 | 0.0% | 2026-06-30 |
|
Delphi
delphi.ai
|
primary | 2 | — | 2026-05-20 |
|
Knocommerce
knocommerce.com
|
primary | 4 | 0.0% | 2026-06-22 |
IPs we've observed sending via Customer.io. "Brands" = distinct brands seen on each IP; "Placement" = where those emails landed in Gmail (inbox / promotions / spam). Click "reputation" to check the IP on Cisco Talos.
| IP | Hostname | Brands | Obs | Placement | Reputation |
|---|---|---|---|---|---|
| 159.112.243.54 | v554.v5be21903.use4.send.mailgun.net |
9 | 69 | 8 | Check → |
| 143.55.227.66 | v566.v54f91261.use4.send.mailgun.net |
1 | 43 | 1 | Check → |
| 161.38.193.2 | v52.v56f0a4e3.use4.send.mailgun.net |
4 | 22 | 4 | Check → |
| 198.244.52.106 | a106.a355d2fe.use4.send.mailgun.net |
1 | 18 | 1 | Check → |
| 198.244.52.3 | a3.a355d2fe.use4.send.mailgun.net |
9 | 18 | 2 | Check → |
| 69.72.44.6 | v56.v5e5d4d68.usw1.send.mailgun.net |
1 | 18 | — | Check → |
| 143.55.227.79 | v579.v54f91261.use4.send.mailgun.net |
5 | 17 | 7 | Check → |
| 161.38.193.1 | v51.v56f0a4e3.use4.send.mailgun.net |
3 | 16 | 6 | Check → |
| 141.193.32.214 | v5214.v5ed9ac7d.euw1.send.eu.mailgun.net |
5 | 16 | 8 | Check → |
| 161.38.205.175 | v5175.v5b52dc11.euw1.send.eu.mailgun.net |
3 | 15 | 3 | Check → |
| 198.244.60.95 | a95.a5d06dfa.euw1.send.eu.mailgun.net |
1 | 14 | — | Check → |
| 161.38.193.3 | v53.v56f0a4e3.use4.send.mailgun.net |
3 | 12 | — | Check → |
| 198.244.52.4 | a4.a355d2fe.use4.send.mailgun.net |
5 | 12 | 3 | Check → |
| 159.112.241.102 | v5102.v5c4dda55.use4.send.mailgun.net |
3 | 11 | 12 | Check → |
| 185.250.238.78 | v578.v5bda8fb2.euw1.send.eu.mailgun.net |
6 | 11 | 10 | Check → |
| 161.38.193.11 | v511.v56f0a4e3.use4.send.mailgun.net |
1 | 11 | 2 | Check → |
| 198.244.60.119 | a119.a5d06dfa.euw1.send.eu.mailgun.net |
1 | 10 | 2 | Check → |
| 69.72.44.2 | v52.v5e5d4d68.usw1.send.mailgun.net |
3 | 10 | 4 | Check → |
| 143.55.227.74 | v574.v54f91261.use4.send.mailgun.net |
3 | 10 | 13 | Check → |
| 161.38.193.4 | v54.v56f0a4e3.use4.send.mailgun.net |
3 | 10 | 3 | Check → |
| 143.55.233.26 | v526.v596efc78.use4.send.mailgun.net |
1 | 9 | 1 | Check → |
| 198.244.60.15 | a15.a5d06dfa.euw1.send.eu.mailgun.net |
1 | 8 | — | Check → |
| 159.112.241.115 | v5115.v5c4dda55.use4.send.mailgun.net |
3 | 8 | — | Check → |
| 161.38.196.32 | v532.v5ab752a9.usw1.send.mailgun.net |
1 | 8 | — | Check → |
| 159.135.236.104 | v5104.v51a3e4cb.usw1.send.mailgun.net |
1 | 8 | — | Check → |