Mailock® With M365

Protect M365

email exchanges

Deliver critical information securely

Encrypt and set authentication challenges for emails sent in M365. Provide company-wide protection for critical email exchanges.

Customer service rep securing emails with Mailock

Microsoft 365 integration

Secure email tightly integrated with M365

Use our Outlook add-in for desktop secure email or our secure email gateway for company-wide protection and scaled delivery.

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

Recipient authentication

Challenge recipients,

protect information

Add multi-factor authentication to your M365 emails. Use SMS, question-and-answer, or Unipass ID challenges to verify recipients 'are who they say'.

SMS identity challenge mailock

Unilateral revoke

Revoke you

can rely on

While you can recall an email in certain scenarios using M365's native tools, it's down to the recipient to accept. Mailock revokes sensitive emails every time.

Revoked secure email with Mailock

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 to send it securely.

Trigger word alert-1


M365 & Mailock



M365 Microsoft Purview Message Encryption

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

What's M365's

email encryption?

Top tier Microsoft 365 plans (e.g., E5) offer customers access to Microsoft Purview Message Encryption (MPME), part of the Azure Information Protection (AIP) suite. It uses email encryption to reduce the chance of an email getting intercepted.

Securing Client Communications At Thanks Wealth Planning-2-1

When 365 isn't enough

As the team at Microsoft say, AIP is only designed to be used "to prevent accidental misuse and is not a security boundary." It lacks the authentication capabilities required to ensure delivery to the intended recipient and Microsoft actively discourages the use of encryption at high volumes.

Office setting with staff working-1

Regulatory compliance

Fulfil your obligations

Protect data in line with regulatory guidance


"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.”


Mailock removes a lot of 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
IFA in meeting with client business about data

Easy Integration

Plug 'n' play

secure comms

Mailock works 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


Protect M365 email.
Free your comms.

Turn email into a secure communications channel that drives customer engagement, efficiency, and carbon 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 themselves 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's about to be sent unsecured.

Audit trails

Senders and administrators can view audit trails displaying send, read access, and download timestamps.

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

Tap into the Mailock API for accurate open rate and attachment download analytics to report on.

High volume delivery

High-volume delivery means no imposed hard ceilings on message volume or throughput.



Add multiple tenants to a single appliance to deliver secure email on behalf of multiple domains/brands.

Custom branding

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

Scaled delivery

Send secure email

at high volume

Do you need to secure email exchanges between contact centre and customer, or switch your confidential output from print-and-post to digital delivery, securely? There is no imposed hard ceiling on volume for Mailock Automated customers.

Man on phone using laptop (1)

Download the Complete Mailock & Microsoft 365 Guide

team sitting in common area in meeting

Increase efficiency

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

weekend volunteers recycling in the park (3)

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 review: M365 secure email vs Mailock

Read our review comparing Microsoft 365's secure email features with Mailock.

Case studies

  Hear from our users

6 min read
Rapport financial strategists
05 05 23

Boosting Security And Engagement At Rapport Financial Strategists

This case study shows how Rapport Financial Strategists improved the security and effectiveness of their client communications using Mailock secure email.

2 min read
Woman speaking to colleague in office about email security
22 02 23

Brearley Law Puts The Protection Of Client Data First With Mailock

According to the most recent ICO statistics, the UK legal industry is responsible for 8% of total data breach incidents reported in the past year.

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.