The 6 most secure email clients for teams

There are lots of secure email clients on the market—Tutanota, ProtonMail, StartMail. But many of these fail to have the helpful collaborative features of more modern business email clients. Where you can have internal comments, real-time drafting, powerful automations, all in an intuitive interface. 

Tutanota - Tutanota is a top tier secure email provider. It offers end-to-end encryption, send encrypted emails, but zero collaborative functionality or third-party integrations. 

ProtonMail - ProtonMail is a close competitor to Tutanota. It allows you to send password-protected encrypted emails, open source mobile apps, but no collaborative features.  

StartMail - StartMail is another secure email provider. It offers local storage with ISO 27001 certified data centers and out of the box phishing and spam protection, but like the other two options, it has little collaborative functions. 

If you just need a few shared labels, email aliases, and calendars to make your team more productive, then any of these options would work great. But if you often have multiple team members working on email threads and/or high volumes of emails that need to be coordinated amongst multiple people—you'll want to look into true collaborative email clients. 

If you rely on email for your business and you work with sensitive information, you'll want to know which of these shiny collaborative email clients have robust security and privacy standards underneath the hood.

Note: If you require a very high level of privacy like PGP, you're better off with one of the traditional options (i.e. Tuta) or Mailfence/Posteo/Zoho Mail for small businesses. But if PGP and full end-to-end encryption is not required, then keep reading on...

We looked at 6 of the most popular email clients for teams on the market, and scored them on 6 criteria: 

• Security hygiene: The basics done right: encryption in transit/at rest, hardened cloud, secure SDLC, vulnerability handling. Shared mailboxes or delegated access without handing out the actual password. 
• Auditing & accountability: A paper trail of who accessed, forwarded, or deleted an email—crucial for compliance and insider risk. Security/audit logs, permission-change trails, labeling/IRM options.
• Access, removal, and sign-in controls: Ability to restrict logins by IP address or location. Quick removal of access when an employee leaves, without disrupting others. SAML/SCIM/Okta/Entra/Google SSO, two factor authentication, hardware keys, role granularity.
• Privacy & data handling: What’s stored (email content vs. limited metadata), AI/LLM data use, DPAs/BAAs.
• External verification: Third-party attestations like SOC 2 Type II, ISO 27001, CASA Tier 2, Google OAuth verification, regular audits. 
• Data residency: Ability to keep data in specific regions (multi-geo, customer-selectable locations).

As a benchmark, we compared each of them to the gold standard of secure email providers and email security—Outlook/Microsoft 365. 

Let's get into it. 

Outlook—the gold standard

Outlook is the most popular email service and email client for enterprises, especially those who deal with sensitive client information over email. Outlook has unmatched configuration options and incredibly detailed auditability.

Auditability is particularly important for professional industries like healthcare, finance, and public sector companies which have recording keeping requirements by law. Here's Outlook's score: 

• Security hygiene (10): Mature encryption choices (S/MIME and Microsoft Purview Message Encryption) for internal and external recipients.
• Auditing (10): Unified Audit Log covers user/admin/mailbox actions with exportable detail. 
• Access/removal (10): IP/country restrictions via Conditional Access, rapid token revocation and account disable for offboarding.
• Privacy (9): Enterprise-grade controls; effectiveness depends on your DLP/labels/retention configuration.
• External verification (10): Broad Microsoft compliance portfolio (SOC/ISO, etc.) and admin docs.
• Data residency (10): Multi-Geo lets you place mailbox data per user.

Bottom line: There's a reason why Outlook is the email service of choice for enterprises. Now, if only they could do collaboration well.

Missive—best secure email for team collaboration

Missive is a collaborative inbox designed for teams that supports all email service providers, including IMAP accounts. While it doesn't offer end-to-end encryption, it does have very high security standards, auditability, and external verification.‍

• Security hygiene (9): All data, including emails, files, and internal comments, is encrypted at rest and in transit. All emails and their attachments are stored on your email provider’s servers. Ongoing hardening and a published Vulnerability Disclosure & Reward program.
• Auditing (8): Practical admin features (roles/permissions, IP restrictions on higher tiers); retains full history of internal chats and comments.
• Access/removal (9): Supports Single Sign-On (SSO) using any SAML-based identity provider (IdP). IP restriction, multiple roles/permissions. When you remove someone from your organization, they immediately stop having access to any conversation shared with them.
• Privacy & data handling (8): GDPR-ready. Credentials for external accounts are encrypted and managed using an industry-standard Hardware Security Module (HSM).
• External verification (9): SOC 2 Type II compliant.
• Data residency (6/10): All customer data is stored in the United States, hosted on Amazon Web Services (AWS).

Price: Starts at $14/user/month, paid annually. 

Bottom line: Missive checks the boxes that most teams look for (SSO, SOC 2, TLS encryption) and is clear in public docs. Audit depth & residency options aren’t M365-level, hence the gap. 

Superhuman—best secure email with read receipts

Superhuman is a productivity-first email service build for high volume inboxes who loves shortcuts. It offers less collaboration functionality than others on this list, but it shines on it's  access/removal functionality. By default, Superhuman does insert a pixel in all emails for it's read receipt feature, that might be a privacy concern for some. 

• Security hygiene (8): Enterprise posture; Google Advanced Protection supported.
• Auditing (7): Centralized oversight and admin controls; but no audit trail and not nearly as deep as Microsoft’s unified audit coverage. 
• Access/removal (10): SAML + SCIM + MDM, plus SSO via Google/Microsoft/Okta. 
• Privacy (7): Privacy policy describes processing of email-related data to provide features; evaluate scopes. 
• External verification (9): SOC 2 Type II and ISO/CCPA/GDPR compliant. 
• Data residency (6): No self-serve residency picker. 

‍Price: Starts at $25/user/month, paid annually.

‍Bottom line: If you already run Okta/Entra and need fast onboarding/offboarding, Superhuman’s Identity and Access Management system is excellent. Balance that with the privacy policy’s scope.

Hiver—best secure email for Gmail-interface lovers

Hiver started is the Gmail-only option on this list. It has a a lot of the collaborative email functions like Missive but most of their customers use it as an alternative to a help desk. Here's how they rank from a security perspective: 

• Security hygiene (9): Does not store emails (keeps limited metadata); brief encrypted staging for sync.
• Auditing (8): Exposes an activity timeline/reporting and analytics for shared mailboxes (on top of Gmail logs). 
• Access/removal (7): Roles/permissions and instant Hiver offboarding; IP-based login restriction isn’t offered by Hiver (rely on Google security & CA).
• Privacy (9): Hiver emphasizes operating within Gmail; earlier materials highlight minimal extra content storage.
• External verification (9): SOC 2 Type II and ISO 27001 complaint.
• Data residency 7 — Follows Google Workspace hosting; no independent region picker.

Price: Starts at $19/user/month, paid annually.

Bottom line: If your priority is “don’t duplicate email content in another vendor,” Hiver is attractive for Google Workspace shops.

Shortwave—best secure email with deep AI features

Shortwave is the most AI-forward email service on this list. They don't excel at any security standard compared to the other options, but they're a good middle ground option if you're looking for some thing with a lot of AI functionality and you're not required to have solid audit logs. 

• Security hygiene (9): All data on Google Cloud, encrypted at rest/in transit. Collaboration avoids password sharing (no “delegated inbox,” but team sharing of threads). 
• Auditing (5): No detailed audit trails for individual actions like forwarding/deletion.
• Access/removal (8): Auth via Google OAuth; benefits from Google 2FA/passkeys and Advanced Protection; team owners can remove members from Settings → Members & Billing. 
• Privacy (9) Limited sub-processors, no third-party LLM training claims on site.
• External verification (8): CASA Tier 2, but not SOC 2 Type II compliant.  
• Data residency (6): Hosted on GCP; no customer-selectable residency.

Price: Starts at $24/user/month, paid annually.

Bottom line: Great in Google-first orgs, but if you need audit trails for compliance/forensics for your industry, you'll probably want a different option. 

Spark—best secure email for minimal requirements

Spark is used by individuals and teams. They offer a familiar interface with some collaboration functionality, though they are the lightest security option on this list.  

• ‍Security hygiene (9): Push notifications use encrypted payloads deleted ~4 hours after send; “Send Later” stores messages encrypted until delivery. Hosted on GCP. ‍
• Auditing (6): Audit trails come via Google Admin/Gmail logs rather than inside Spark. So like Shortwave, no audit trail functionality within Spark. ‍
• Access/removal (6): Quick offboarding and strong auth (Google 2FA/passkeys/SSO), but no IP/location login restrictions in Spark today. ‍
• Privacy (7): Clear docs on notification/scheduling storage windows; Spark +AI uses Azure OpenAI with Microsoft’s data protections. ‍
• External verification (5): Not SOC 2 compliant yet (in progress).‍
• Data residency (5): GCP-hosted; no customer region picker published.

Price: Starts at $4.99/month for individuals and $6.99/user/month for teams, paid annually.

Bottom line: Individual teams that want a polished client and understand the implications of server-side features for notifications/scheduling.

Use the scorecard like a buyer, not a auditor

1. Pick your “non-negotiables.”
   If you need in-region storage or multi-geo, Outlook wins today. If your priority is not storing email content in a third-party tool, all of these tools would work.
2. Map IAM to how your team works.
   Already on Okta or Entra? Favor clients with SAML/SCIM so onboarding/offboarding stays tight (Missive, Superhuman). 
3. Decide how much “paper trail” you need.
   If audits and forensic trails matter (e.g., legal/finance), Outlook’s unified audit log is hard to beat, but Missive's auditability is highest amongst the rest. 
4. Understand AI data paths.
   Shortwave publishes a limited sub-processor list and “no 3rd-party LLM training” stance; Spark +AI routes requests per its policy; Missive documents Google OAuth verification. Pick the path you’re comfortable with. 

Tuta, ProtonMail or even Zoho Mail has a lot of the enterprise-grade security features (encrypted mail, PGP, etc) right out of the box, but the collaborative-first email clients we mentioned here might be able to meet your security standards with a little custom development. For example, you can feed all of the data/comms out to a third-party compliance service to make sure you hit the regulatory requirements. 

At the end of the day, it'll depend on what trade offs you're willing or unwilling to make. Most businesses want some level of security but also usability and collaboration. How much of each will depend greatly on your use case.

Email Security FAQ for busy owners

Which of these options offer end-to-end encryption and encrypted emails?

Short answer is none. While most of these options have some form of encryption, the higher scoring ones are encrypted via TLS at rest and in transit, but none of them offer the same level of encryption features as Tuta or ProtonMail. 

Is Outlook “more secure” than these tools?
It’s more controllable out of the box—especially for audit, labeling/IRM, and data residency. That’s why we use it as the baseline. Your best option is the one that fits your constraints and is configured well. 

Do these tools read my emails?
Policies differ. Some tools process email content to power features (e.g., read receipts, scheduling, AI summaries). Some store only metadata. Always confirm what’s stored and for how long. 

Are there other options with different encryption options?

If you're primarily looking for encryption features, but don't want to go with your standard Tuta, then you might want to check out Zoho Mail, Mailfence, or Posteo. The latter options offer OpenPGP end-to-end encryption and the former is basically enterprise level controls that isn't Outlook. 

Remember the first time you @mentioned a teammate below an email, instead of forwarding it to them?

That’s a magical moment for many Missive users.

It’s when they realized email can be collaborative without creating more email.

Starting today, with Guest Access, you can give that same experience to anyone you work with — even if they’re not on your team.

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Invite third-party collaborators into the conversation

Guest Access makes it easy to bring people outside your organization — like an accountant, contractor, or client — directly into specific Missive conversations.

No more forwarding long threads. No more stitching together feedback from different tools. Just real-time chat alongside the emails that matter.

Here’s how it works:

• Go to a conversation
• Click the access menu → Invite guest
• Enter their email and send the invite

Your guest will get an email with a link to join. Once they create a free Missive account, they’ll land directly in the conversation you invited them to.

They’ll be able to read the full message history and reply via chat — but not email, tasks, or assignments. Just focused, limited access.

What you get (and don’t pay extra for)

Guest Access is included in all Missive plans. No add-ons. No hidden costs.

Each team member can invite up to 5 guests, and each guest can access up to 5 conversations.

That means if your team has 10 users, you can collaborate with up to 50 guests across 250 guest-enabled conversations — all for free.

A better way to loop in “sometimes” collaborators

We designed Guest Access for the people you don’t work with every day, but still need to collaborate with effectively — without paying for a full seat or dragging another tool into the mix.

If you’ve ever said:

I wish this person could just see this conversation—now they can.

Guest Access isn’t just for external vendors or partners. If you have teammates who don’t need full Missive functionality every day, Guest Access is a perfect lightweight option. No need to buy a full seat just to loop someone in occasionally.

Admins stay in control

By default, any team member can invite guests. But admins can manage this in:

Settings → Guests → Allow guest invitations

You can:

• Disable Guest Access across your org
• Restrict invitations to only admins or the org owner
• View and manage a list of all active guests
• See which conversations guests are part of
• Revoke access individually to stay within your limits

Want tighter control? You can restrict guest invitations so only admins or the org owner can send them. That way, access stays centralized and intentional.

What guests can (and can’t) do

Guests can:

• View the full message history of the conversation they’re invited to
• Chat in the conversation

Guests cannot:

• Reply to emails
• Be assigned to tasks
• Create tasks
• Access conversations they weren't explicitly invited to

This keeps their access simple, focused, and secure.

Need to make space? It’s easy.

Admins can see which guests are active and what they have access to. If you need to invite new guests but hit your limit, you can quickly revoke access from inactive ones to free up slots.

We can’t wait to see how you use Guest Access.

Whether you’re looping in a freelance designer, a tax advisor, or just a teammate who doesn't need a full Missive seat — Guest Access gives you the power to collaborate where the conversation is happening.

Try it today and let us know what you think!

Frequently Asked Questions

Can guests see the full history of the conversation?
Yes. Guests can view the entire message and chat history of any conversation they’re invited to.

Can guests reply to emails or send new ones?
No. Guests can only send chat messages. They cannot interact with the email side of the conversation.

Can guests be assigned to tasks or create tasks?
No. Guests don’t have access to task-related features in Missive.

Can guests @mention team members?
Yes. Guests can use @mentions in the chat area of the conversation to address specific people already present in the conversations. They can’t @mention people not present in the conversation.

What happens if I remove a guest from a conversation?
They will instantly lose access to that conversation and all its content.

Can I re-invite someone after removing them?
Absolutely. You can revoke access at any time and re-invite them later if needed.

Can I upgrade a guest to a full team member later?
Yes. If someone needs broader access, you can always add them as a regular user by assigning them a seat.

What if my guest has their own Missive organization?
They will be able to access the conversation(s) that you granted them, from their existing Missive interface. It will be treated like any other conversation.

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