DuoCircle vs Customer.io Comparison (2025)

What are the differences between DuoCircle and Customer.io?

Forward Email Team
Written by
Forward Email TeamVerified
Published
7/1/25
Time to read
Less than 5 minutes
We recommend Forward Email as the best alternative to DuoCircle.

Email Service Comparison

20 facts in comparison
DuoCirclevs.Customer.io

DuoCircle

Protect Email Against Phishing, Spam and Malware
"Protect Email Against Phishing, Spam and Malware"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
vs.

Customer.io

Send messages people actually want to receive using real-time customer data
"Send messages people actually want to receive using real-time customer data"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
Requires you to talk to a sales teamPricing$100/mo
Requires 3rd partyStorageNo Customer.io does not support storage
50 MBAttachments2 MB
NoOpen-SourceNo
NoSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
❌ Requires 3rd partySMTPYes
❌ Requires 3rd partyIMAPNo
❌ Requires 3rd partyPOP3No
YesAPIYes
NoE2EE No
NoOpenPGP No
NoWKD No

Email Service Screenshots

Closed-source

DuoCircle

DuoCircle is a closed-source email service. Their official description reads: Protect Email Against Phishing, Spam and Malware

DuoCircle is a closed-source email service.
Photograph by Forward Email
Go to site
Closed-source

Customer.io

Customer.io is a closed-source email service. Its description from its website is: Send messages people actually want to receive using real-time customer data

Customer.io is a closed-source email service.
Photograph by Forward Email
Go to site

Compare DuoCircle with 78 email services