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Cybersecurity · head to head

Cisco Duo vs Proton Mail

Cisco Duo logo

Cisco Duo

Cybersecurity

Trusted access for all users, all devices

From
Free
Rated
-
Full reviewWebsite
Proton Mail logo

Proton Mail

Cybersecurity

Secure email that protects your privacy

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Cisco Duo free tier limited to 10 users maximum; Proton Mail paid plan pricing not displayed on vendor site
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Cisco Duo and Proton Mail actually diverge.

Attributes where Cisco Duo and Proton Mail differ
AttributeCisco DuoProton Mail
Pricing modelsubscriptionfreemium

Identical on both: starting price (Free), free tier (Yes), platforms (Web), user rating (Not yet rated), category (Cybersecurity).

What people use each for

The jobs each tool is most often brought in to do.

Cisco Duo

  • Eliminating phishing with passwordless authnot Proton Mail
  • Implementing zero trust with device trustnot Proton Mail
  • Protecting sessions from hijacking and theftnot Proton Mail
  • Managing compliance for regulated industriesnot Proton Mail

Proton Mail

  • Encrypted email communicationnot Cisco Duo
  • Privacy-focused email servicenot Cisco Duo
  • Family email protectionnot Cisco Duo

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Cisco Duo

  • Free tier limited to 10 users maximum
  • Licenses must be purchased in 10-user increments (under 100 users) or 25-user increments (100+ users)
  • Pricing is per-user per-month with minimum purchase increments

Proton Mail

  • Paid plan pricing not displayed on vendor site
  • Free tier limited to 1 GB storage
  • Free tier limited to single email address

Pricing, plan by plan

Cisco Duo

Free
  • FreeFree
    • Multi-factor authentication (MFA)
    • Seamless integrations
    • Authenticator app
  • Essentials$3/month
    • All Free features
    • Duo Directory
    • Phishing-resistant MFA
  • Advantage$6/month
    • All Essentials features
    • Identity intelligence
    • Cisco Identity Intelligence (ISPM, ITDR)
  • Premier$9/month
    • All Advantage features
    • Complete device trust
    • VPN-less remote access

Proton Mail

Free

No published plan breakdown. See the Proton Mail review.

Which should you pick?

Choose Cisco Duo if

  • You want to start without paying.
Cisco Duo review

Choose Proton Mail if

  • You want to start without paying.
Proton Mail review

Questions people ask

Is Cisco Duo or Proton Mail better?
Neither clearly leads. Cisco Duo starts at Free and Proton Mail at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cisco Duo or Proton Mail?
Cisco Duo starts at Free and Proton Mail at Free.
Does Cisco Duo or Proton Mail run on more platforms?
Both run on Web, so platform support will not decide this one for you.
Can I use Cisco Duo for free?
Both have a free tier, so you can try either at no cost before committing.
What is Cisco Duo best used for?
Cisco Duo is most often used for eliminating phishing with passwordless auth, implementing zero trust with device trust, protecting sessions from hijacking and theft, managing compliance for regulated industries. Of those, eliminating phishing with passwordless auth and implementing zero trust with device trust are not what Proton Mail is typically brought in for.

Answered from the vendors’ own pages

Cisco Duo: How much does Cisco Duo cost?

Cisco Duo Free is $0/user/month (up to 10 users). Paid plans start at $3/user/month (Essentials), $6/user/month (Advantage), and $9/user/month (Premier). Billing is per-user per-month.

Source
Proton Mail: Is there a free version of Proton Mail?

Yes, Proton Mail offers a free plan with 1 GB storage, 1 encrypted email address, and basic features like folders, labels, and filters.

Source
Cisco Duo: Is Cisco Duo free to try?

Yes, Duo Free offers multi-factor authentication and seamless integrations at $0/user/month for up to 10 users.

Source
Proton Mail: What does the Mail Plus plan include?

Mail Plus includes 15 GB storage, 10 encrypted email addresses, support for 1 custom domain, 10 hide-my-email aliases, priority support, and access to Proton Calendar.

Source
Cisco Duo: What is the minimum purchase for Cisco Duo?

Organizations must buy licenses in 10-user increments for under 100 users, or 25-user increments for 100 or more users. Plans are modifiable at any time.

Source
Proton Mail: What is included in Proton Unlimited?

Proton Unlimited provides 500 GB storage, 15 email addresses, 3 custom domains, unlimited hide-my-email aliases, access to Mail, Calendar, VPN, Drive, and Pass, plus dedicated support.

Source
Cisco Duo: What does the Advantage plan add over Essentials?

Advantage ($6/user/month) adds identity intelligence, Cisco Identity Intelligence (ISPM, ITDR), Duo Passport, session theft protection, Active Directory Defense, and risk-based authentication.

Source
Proton Mail: Does Proton Mail offer a money-back guarantee?

Yes, Proton Mail provides a 30-day money-back guarantee for paid plans.

Source
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