Heimdal vs Proton Mail Comparison (2025)

What are the differences between Heimdal 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 Heimdal.

Email Service Comparison

20 facts in comparison
Heimdalvs.Proton Mail

Heimdal

One Platform. Total Security.
"One Platform. Total Security."
  • 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
Requires you to talk to a sales teamPricing$3.99/mo
Requires 3rd partyStorage15 GB
UnknownAttachments25 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
❌ Requires 3rd partySMTP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
❌ Requires 3rd partyIMAP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
❌ Requires 3rd partyPOP3❌ Proton Mail does not support POP3
YesAPINo
NoE2EE ⚠️ Proton Mail rewrites your emails
NoOpenPGP Yes
NoWKD Yes

Email Service Screenshots

Closed-source

Heimdal

Heimdal is a closed-source email service. Their website says: One Platform. Total Security.

Heimdal 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. Their official description reads: Secure email that protects your privacy

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

Compare Heimdal with 78 email services