Customer.io vs Spam Hero Comparison (2025)

What are the differences between Customer.io and Spam Hero?

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 Customer.io.

Email Service Comparison

20 facts in comparison
Customer.iovs.Spam Hero

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
vs.

Spam Hero

Cloud-Based Spam Filtering
"Cloud-Based Spam Filtering"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
$100/moPricing$8/mo
No Customer.io does not support storageStorageRequires 3rd party
2 MBAttachments50 MB
NoOpen-SourceNo
NoSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
YesSMTP❌ Requires 3rd party
NoIMAP❌ Requires 3rd party
NoPOP3❌ Requires 3rd party
YesAPIYes
NoE2EE No
NoOpenPGP No
NoWKD No

Email Service Screenshots

Closed-source

Customer.io

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

Customer.io is a closed-source email service.
Screenshot by Forward Email
Visit Website
Closed-source

Spam Hero

Spam Hero is a closed-source email service. According to their website: Cloud-Based Spam Filtering

Spam Hero is a closed-source email service.
Photo by Forward Email
Visit Website

Compare Customer.io with 78 email services