SMTP.com vs Customer.io Comparison (2026)

What are the differences between SMTP.com and Customer.io?

Forward Email Team
Written by
Forward Email TeamVerified
Published
2/1/26
Time to read
Less than 5 minutes
We recommend Forward Email as the best alternative to SMTP.com. We also support webmail: https://mail.forwardemail.net

Email Service Comparison

20 facts in comparison
SMTP.comvs.Customer.io

SMTP.com

Transactional and email relay API
"Transactional and email relay API"
  • 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
$25/moPricing$100/mo
No SMTP.com does not support storageStorageNo Customer.io does not support storage
15 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

SMTP.com

SMTP.com is a closed-source email service. Their website says: Transactional and email relay API

SMTP.com is a closed-source email service.
Screenshot 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 SMTP.com with 78 email services