Mailock® For M365

Outbound email

security for M365

Deliver securely with Microsoft 365

Extend M365 to exchange sensitive information by email with the confidence that only the right people can gain access.

Hero graphic 365 (1)

Microsoft integration

Tightly integrated

with Microsoft 365

Use our Windows Outlook add-in to send and receive secure emails from your desktop. Integrate our secure email gateway with your 365 Exchange for company-wide protection and high volume digital delivery.

  • Desktop add-in for individual secure emails
  • Exchange integration for high-volume delivery
Oultok ribbon bar Mailock faded-1

What's M365's Encryption?

Top tier Microsoft 365 plans (e.g., E5) offer customers access to Microsoft Purview Message Encryption (MPME), part of the Azure Information Protection suite. MPME uses email encryption to increase the chance of an email reaching the right person without it being intercepted.

Compliance Checklist Financial Services Outbound Email

When MPME isn't enough

As our partners at Microsoft say, the rights management suite is designed to be used "to prevent accidental misuse and is not a security boundary." They also discourage the delivery of encrypted email at high volumes, with rate limits designed to curtail usage.

Professionals in office having a heated discussion at desk

Recipient authentication

Challenge recipients

protect information

Mailock expands Microsoft's native capability to verify recipient inbox access with identity authentication that proves they 'are who they say they are'.

  • SMS: Send a one-time-code
  • Q&A: Ask a custom question
  • Unipass ID: Authenticate Unipass ID
SMS identity challenge mailock

Unilateral revoke

Revoke you

can rely on

While you can request to revoke an encrypted email (in certain scenarios) using Microsoft's native tools, it's down to the sender to accept. Mailock revokes secure emails unilaterally to lock down breaches.

Access details in Outlook for M365

Trigger words

'Before you send'

breach prevention

Customise our preset list of trigger words, which, if present in an unsecured email, will surface a prompt asking you to secure it. Build a data loss protection profile that reflects your security policy.

Trigger word alert-1

Scaled delivery

Send secure email

at high volume

Whether you need to secure email exchanges between your contact centre and customers or switch your confidential print-and-post output to secure email, Mailock can keep your communications secure. There are no imposed limits on volume or throughput for secure email sent using our network.

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Fulfil your compliance obligations


"Have a policy governing encrypted email, including guidelines that enable staff to understand when they should or should not use it. For example, there may be a guideline stating that any email containing sensitive personal data (either in the body or as an unencrypted attachment) should be sent encrypted."

"[in the event of a data breach] act quickly. Try to recall the email as soon as possible. If you can’t recall it, contact the person who received it and ask them to delete it. The 72 hours following a personal data breach are particularly critical."


"Keep a copy of relevant electronic communications, made with, sent from or received on equipment: (1) provided by the firm to an employee or contractor; or (2) the use of which by an employee or contractor has been sanctioned or permitted by the firm."


"Have sound security mechanisms in place to guarantee the security and authentication of the means of transfer of information, minimise the risk of data corruption and unauthorised access and to prevent information leakage maintaining the confidentiality of the data at all times.”


At a glance

M365 vs Mailock



Prevent email interception
End-to-end encryption
Recipient authentication
Trigger words
Audit trails
Message revoke
Read notifications
Engagement analytics
High volume delivery

Easy Integration

Plug 'n' play

secure comms

Mailock is designed to work seamlessly with other 365 integrations, leaving your emails accessible to data loss prevention and server-side signature tools.

  • On-premise deployment support
  • Fully managed cloud service
Sending a secure email

Secure replies

Empower customers

to reply securely

Recipients can read messages and download attachments without creating an account, then connect their email to reply for free.

  • Customers read-and-reply free
  • Read-without-registration
Recipients can reply securely

The recipient experience

1. Receive

Recipients receive a notification email to let them know they have a secure message waiting to be opened. This message can be customised with your company branding or use the familiar Mailock template.

Secure notification message

2. Identify

Recipients click ‘Open’ on the notification delivered to their inbox. They’ll answer any challenges that have been set, or if they're trusted, they can open and read right away.

Enter the code to unlock your secure email

3. Reply

If recipients need to reply to a secure message, they can use Mailock to compose, attach, and send using their existing email address and account. They'll even get a limited number of secure emails to send.

Secure read pane in Mailock web app
Secure notification message
Enter the code to unlock your secure email
Secure read pane in Mailock web app


Mailock removes a lot of the risk and GDPR concern

around dealing with everyone’s favourite communication method - email. We can send and receive our clients' information safely.

 Rob Hastings  Harwell Finance Group
Mailock removes a lot of the risk


Protect email data.
Free your comms.

Turn email into a secure communications channel that drives customer engagement, efficiency, and cost savings.


End-to-end encryption

AES-256 end-to-end encryption obscures message and attachment data using military-strength ciphers.

Recipient authentication

Require recipients to authenticate their identity to open a secured message (e.g., SMS, Q&A, Unipass ID).

Trigger words

Set custom keywords that trigger a warning if they appear in an email that could be sent unsecured.

Audit trails

Senders and administrators can view audit trails displaying timestamps of sends, read access, and downloads.

Message revoke

Administrators and senders can revoke access to secure emails regardless of recipient infrastructure.

Read notifications

Read notifications tell senders when secure emails are opened regardless of recipient infrastructure.

Engagement analytics

Administrators can access accurate open rate and attachment download analytics for reporting.

High volume delivery

Support for high-volume delivery means no hard ceiling on message volume or message throughput.



Add multiple brand instances to a single appliance for the delivery of secure email using multiple brands.

Custom branding

Persist your branding throughout the secure email read experience, from email notification to our web app.

Download the Mailock
Enterprise Data Sheet

Make an impact

Turn email into your greatest power

Transform communications, meet business goals, and make email a force for good.

team sitting in common area in meeting

Increase efficiency

Save time spent sending sensitive information back and forth between colleagues, partners, and clients. Speed is key to a positive customer experience according to PWC reports.

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Save paper

Let’s reach Net Zero goals together, with innovation. Reduce your paper document output by taking sensitive document exchanges digital. Save carbon and do it with bottom line impact.

Woman in office securing professional emails on laptop at desk (1)

Protect data

Free your business from open-risk email. Protect messages and files from cyber threat and human error. Exchange documents with customers and keep their data safe in line with GDPR.

Mailock vs Microsoft 365 encryption blog hero-1

Mailock compared

Read the full review: M365 encryption vs Mailock

Read our article comparing Microsoft's Purview Message Encryption with Mailock for secure customer communications.

Case studies

  Hear from our users

2 min read
Securing Client Communications At Stonebridge Financial
21 12 22

Securing Client Communications At Stonebridge Financial

Find out how Stonebridge Financial secured their email communications using Mailock, driving efficiency and engagement with their clients in the process.

3 min read
Securing Client Communications At Thanks Wealth Planning
11 11 22

Securing Client Communications At Thanks Wealth Planning

Personal information is abundant within financial services. This case study shows how Thanks Wealth Planning increased security for their communications.

3 min read
How Mailock Secures Sensitive Emails At Genius Wealth Management
22 07 22

How Mailock Secures Sensitive Emails At Genius Wealth Management

How Mailock Secures Sensitive Emails at Genius Wealth Management. Did you know that 70% of financial firms in the UK experienced cyberattacks in 2020?