Proton Mail vs Cisco Secure Email Defense Comparison (2025)

What are the differences between Proton Mail and Cisco Secure Email Defense?

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 Proton Mail.

Email Service Comparison

20 facts in comparison

Proton Mail	vs.	Cisco Secure Email Defense
Proton Mail "Secure email that protects your privacy" Website	vs.	Cisco Secure Email Defense "Advanced protection to safeguard your inboxes" Website
$3.99/mo	Pricing	Requires you to talk to a sales team
15 GB	Storage	Unknown
25 MB	Attachments	100 MB
❌ Proton Mail claims to be open-source, but their back-end actually is closed source	Open-Source	No
No	Sandboxed Encryption	No
No	Unlimited Domains	No
No	Unlimited Aliases	No
No	TTI	No
❌ Requires you to download Proton Mail Bridge and forces vendor lock-in	SMTP	❌ Requires 3rd party
❌ Requires you to download Proton Mail Bridge and forces vendor lock-in	IMAP	❌ Requires 3rd party
❌ Proton Mail does not support POP3	POP3	❌ Requires 3rd party
No	API	Yes
⚠️ Proton Mail rewrites your emails	E2EE	No
Yes	OpenPGP	No
Yes	WKD	No

Email Service Screenshots

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

Closed-source

Cisco Secure Email Defense

Cisco Secure Email Defense is a closed-source email service. Its description from its website is: Advanced protection to safeguard your inboxes

Cisco Secure Email Defense is a closed-source email service.

Photograph by Forward Email

Compare Proton Mail with 78 email services