Customer.io vs N‑able Mail Assure Comparison (2025)

What are the differences between Customer.io and N‑able Mail Assure?

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.N‑able Mail Assure

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.

N‑able Mail Assure

Email protection to help you secure and scale
"Email protection to help you secure and scale"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
$100/moPricingRequires you to talk to a sales team
No Customer.io does not support storageStorageRequires 3rd party
2 MBAttachmentsDepends on inbound/outbound (e.g. 10 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.
Photograph by Forward Email
Visit Website
Closed-source

N‑able Mail Assure

N‑able Mail Assure is a closed-source email service. According to their website: Email protection to help you secure and scale

N‑able Mail Assure is a closed-source email service.
Photograph by Forward Email
Visit Website

Compare Customer.io with 78 email services