Updated: April 18, 2025 (April 27, 2024)

Exchange Message Encryption Options

As managing vice president, Rob Helm covers Microsoft collaboration and content management. His 25-plus years of experience analyzing Microsoft’s technology... more

Exchange Online and Exchange Server offer several message encryption options with different capabilities and requirements. The accompanying table shows four methods of message encryption for senders using Exchange Server or Exchange Online:

Purview Message Encryption, enabled by default for Exchange Online customers with qualifying licenses

Office 365 Message Encryption (OME) or legacy OME, the predecessor of Purview Message Encryption, which closed to new tenants since 2023 but has no public retirement date

Information Rights Management (IRM) features of Outlook and Exchange, which predate Purview Message Encryption but are still supported

Secure/Multipurpose Internet Mail Extensions (S/MIME), an Internet standard supported by Outlook and Exchange.

Microsoft will maintain Purview Message encryption, IRM, and S/MIME for the foreseeable future, as each offers a different mix of customer control, reachable recipients, and cost.

Microsoft’s comparison of message encryption methods is at “Comparing email encryption options available in Office 365“.

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