Startmail vs Proton Mail Comparison (2025)

What are the differences between Startmail 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 Startmail.

Email Service Comparison

20 facts in comparison
Startmailvs.Proton Mail

Startmail

Private email you can trust
"Private email you can trust"
  • 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
$7/moPricing$3.99/mo
20 GBStorage15 GB
25 MBAttachments25 MB
NoOpen-Source❌ Proton Mail claims to be open-source, but their back-end actually is closed source
❌ Startmail claims to use a User Vault, but this statement has not been audited and their source code is closed-sourceSandboxed Encryption No
NoUnlimited DomainsNo
NoUnlimited AliasesNo
NoTTI No
YesSMTP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
YesIMAP❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
YesPOP3❌ Proton Mail does not support POP3
NoAPINo
⚠️ Supported if both sender and recipient are using OpenPGPE2EE ⚠️ Proton Mail rewrites your emails
⚠️ Supports OpenPGP, but does not support WKDOpenPGP Yes
NoWKD Yes

Email Service Screenshots

Closed-source

Startmail

Startmail is a closed-source email service. Their website says: Private email you can trust

Startmail is a closed-source email service.
Screenshot by Forward Email
Visit Website
Closed-source

Proton Mail

Proton Mail is a closed-source email service. Its description from its website is: Secure email that protects your privacy

Proton Mail is a closed-source email service.
Photo by Forward Email
Visit Website

Compare Startmail with 78 email services