Proton Mail vs Postmark Comparison (2025)

What are the differences between Proton Mail and Postmark?

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.Postmark

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.

Postmark

The email delivery service that people actually like
"The email delivery service that people actually like"
  • Hardenize Test
  • Internet.nl Site Test
  • Internet.nl Mail Test
  • Mozilla HTTP Observatory Grade
  • Qualys SSL Labs SSL Server Test
$3.99/moPricing$15/mo
15 GBStorageNo Postmark does not support storage
25 MBAttachments10 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 TTI
❌ Requires you to download Proton Mail Bridge and forces vendor lock-inSMTPYes
❌ Requires you to download Proton Mail Bridge and forces vendor lock-inIMAPNo
❌ Proton Mail does not support POP3POP3No
NoAPIYes
⚠️ 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. According to their website: Secure email that protects your privacy

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

Postmark

Postmark is a closed-source email service. Their official description reads: The email delivery service that people actually like

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

Compare Proton Mail with 78 email services