Mailgun vs Customer.io Comparison (2025)

What are the differences between Mailgun 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 Mailgun.

Email Service Comparison

20 facts in comparison
Mailgunvs.Customer.io

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
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
$35/moPricing$100/mo
No Mailgun does not support storageStorageNo Customer.io does not support storage
25 MBAttachments2 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

Mailgun

Mailgun is a closed-source email service. Their website says: Flexible, scalable, and results driven email sending platform

Mailgun is a closed-source email service.
Screenshot by Forward Email
Visit Website
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.
Photograph by Forward Email
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Compare Mailgun with 78 email services