Proton Mail vs Klaviyo Comparison (2025)

What are the differences between Proton Mail and Klaviyo?

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 Proton Mail.

Email Service Comparison

20 facts in comparison
Proton Mailvs.Klaviyo

Proton Mail

Secure email that protects your privacy
"Secure email that protects your privacy"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
vs.

Klaviyo

Power smarter digital relationships
"Power smarter digital relationships"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
$3.99/moPricing$20/mo
15 GBStorageNo Klaviyo does not support storage
25 MBAttachments0 MB
❌ Proton Mail claims to be open-source, but their back-end actually is closed sourceOpen-SourceNo
NoSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
❌ Requires you to download Proton Mail Bridge and forces vendor lock-inSMTPNo
❌ Requires you to download Proton Mail Bridge and forces vendor lock-inIMAPNo
❌ Proton Mail does not support POP3POP3No
NoAPINo
⚠️ Proton Mail rewrites your emailsE2EE No
YesOpenPGP No
YesWKD No

Email Service Screenshots

Closed-source

Proton Mail

Proton Mail is a closed-source email service. Their official description reads: Secure email that protects your privacy

Proton Mail is a closed-source email service.
Screenshot by Forward Email
Go to site
Closed-source

Klaviyo

Klaviyo is a closed-source email service. According to their website: Power smarter digital relationships

Klaviyo is a closed-source email service.
Screenshot by Forward Email
Go to site

Compare Proton Mail with 78 email services