Customer.io vs Mailgun Comparison (2025)

What are the differences between Customer.io and Mailgun?

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.Mailgun

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.

Mailgun

Flexible, scalable, and results driven email sending platform
"Flexible, scalable, and results driven email sending platform"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
$100/moPricing$35/mo
No Customer.io does not support storageStorageNo Mailgun does not support storage
2 MBAttachments25 MB
NoOpen-SourceNo
NoSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
YesSMTPYes
NoIMAPNo
NoPOP3No
YesAPIYes
NoE2EE No
NoOpenPGP No
NoWKD No

Email Service Screenshots

Closed-source

Customer.io

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

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

Mailgun

Mailgun is a closed-source email service. Its description from its website is: Flexible, scalable, and results driven email sending platform

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

Compare Customer.io with 78 email services