Postmark vs Proton Mail Comparison (2025)

What are the differences between Postmark and Proton Mail?

Written by

Forward Email Team

Published

7/1/25

Time to read

Less than 5 minutes

We recommend Forward Email as the best alternative to Postmark.

Email Service Comparison

20 facts in comparison

Postmark	vs.	Proton Mail
Postmark "The email delivery service that people actually like" Website	vs.	Proton Mail "Secure email that protects your privacy" Website
$15/mo	Pricing	$3.99/mo
No Postmark does not support storage	Storage	15 GB
10 MB	Attachments	25 MB
No	Open-Source	❌ Proton Mail claims to be open-source, but their back-end actually is closed source
No	Sandboxed Encryption	No
No	Unlimited Domains	No
No	Unlimited Aliases	No
TTI	TTI	No
Yes	SMTP	❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
No	IMAP	❌ Requires you to download Proton Mail Bridge and forces vendor lock-in
No	POP3	❌ Proton Mail does not support POP3
Yes	API	No
No	E2EE	⚠️ Proton Mail rewrites your emails
No	OpenPGP	Yes
No	WKD	Yes

Email Service Screenshots

Closed-source

Postmark

Postmark is a closed-source email service. Their website says: The email delivery service that people actually like

Postmark is a closed-source email service.

Photograph by Forward Email

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.

Photo by Forward Email

Compare Postmark with 78 email services