Klaviyo vs Proton Mail Comparison (2025)

What are the differences between Klaviyo and Proton Mail?

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 Klaviyo.

Email Service Comparison

20 facts in comparison
Klaviyovs.Proton Mail

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
vs.

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
$20/moPricing$3.99/mo
No Klaviyo does not support storageStorage15 GB
0 MBAttachments25 MB
NoOpen-Source❌ Proton Mail claims to be open-source, but their back-end actually is closed source
NoSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
NoSMTP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
NoIMAP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
NoPOP3❌ Proton Mail does not support POP3
NoAPINo
NoE2EE ⚠️ Proton Mail rewrites your emails
NoOpenPGP Yes
NoWKD Yes

Email Service Screenshots

Closed-source

Klaviyo

Klaviyo is a closed-source email service. Its description from its website is: Power smarter digital relationships

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

Proton Mail

Proton Mail is a closed-source email service. According to their website: Secure email that protects your privacy

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

Compare Klaviyo with 78 email services