check before: 2026-05-01
Product:
Exchange, Microsoft 365 Apps, Outlook, Windows
Platform:
Online, US Instances, Windows Desktop, World tenant
Status:
Rolling out
Change type:
Admin impact, Updated message, User impact
Links:
Details:
Summary:
New Outlook for Windows will support LDAP directories for S/MIME certificate lookup, enabling secure encrypted email with external partners. Rollout begins late May 2026 worldwide, mid-June in GCC. Admins configure LDAP via Exchange Online PowerShell; users add directories in Outlook settings. LDAP must not require authentication.
Details:
Updated May 27, 2026: We have updated the timeline. Thank you for your patience.
[Introduction]
New Outlook for Windows now supports Lightweight Directory Access Protocol (LDAP) directories for S/MIME certificate lookup. This enables tenants to configure LDAP directories for their organization as well as enabling users to configure LDAP directories themselves. Once configured, users can find recipients' public encryption certificates from the directories when sending encrypted email, improving secure collaboration with external partners. This is especially valuable for tenants who collaborate with external partners and rely on public/partner LDAP directories to store public S/MIME certificates of users.
This message is associated with Microsoft 365 Roadmap ID 518287.
[When this will happen:]
General Availability (Worldwide): We will begin rolling out in late May 2026 and expect to complete by mid-June 2026 (previously late May).
General Availability (GCC): We will begin rolling out in mid-June 2026 (previously early June) and expect to complete by late June 2026.
Change Category:
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Scope:
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Release Phase:
General Availability
Created:
2026-05-15
updated:
2026-05-28
Task Type
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Docu to Check
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MS How does it affect me
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MS Preperations
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MS Urgency
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linked item details
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Pictures
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summary for non-techies**
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Direct effects for Operations**
LDAP Configuration Impact
If LDAP directories are not properly configured before the rollout, users may be unable to retrieve public encryption certificates, leading to failed encrypted email communications with external partners.
- roles: Exchange Admins, End Users
- references: https://learn.microsoft.com/exchange/security-and-compliance/smime-exo/configure-smime-exo, https://support.microsoft.com/office/set-up-outlook-to-use-s-mime-encryption-2e57e4bd-4cc2-4531-9a39-426e7c873e26
User Experience Disruption
Without proper preparation, users may face confusion or frustration when trying to send encrypted emails if they cannot find the necessary certificates in the new Outlook, impacting their ability to collaborate securely.
- roles: End Users, IT Support Staff
- references: https://www.microsoft.com/microsoft-365/roadmap?filters=&searchterms=518287, https://learn.microsoft.com/powershell/exchange/connect-to-exchange-online-powershell
Configutation Options**
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IT Security**
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explanation for non-techies**
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** AI generated content. This information must be reviewed before use.
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change history
| Date | Property | old | new |
| 2026-05-28 | MC Messages | Updated May 21, 2026: We have updated the content. Thank you for your patience.
[Introduction] New Outlook for Windows now supports Lightweight Directory Access Protocol (LDAP) directories for S/MIME certificate lookup. This enables tenants to configure LDAP directories for their organization as well as enabling users to configure LDAP directories themselves. Once configured, users can find recipients' public encryption certificates from the directories when sending encrypted email, improving secure collaboration with external partners. This is especially valuable for tenants who collaborate with external partners and rely on public/partner LDAP directories to store public S/MIME certificates of users. This message is associated with Microsoft 365 Roadmap ID 518287. [When this will happen:] General Availability (Worldwide): We will begin rolling out in late May 2026 and expect to complete by late May 2026. General Availability (GCC): We will begin rolling out in early June 2026 and expect to complete by late June 2026. | Updated May 27, 2026: We have updated the timeline. Thank you for your patience.
[Introduction] New Outlook for Windows now supports Lightweight Directory Access Protocol (LDAP) directories for S/MIME certificate lookup. This enables tenants to configure LDAP directories for their organization as well as enabling users to configure LDAP directories themselves. Once configured, users can find recipients' public encryption certificates from the directories when sending encrypted email, improving secure collaboration with external partners. This is especially valuable for tenants who collaborate with external partners and rely on public/partner LDAP directories to store public S/MIME certificates of users. This message is associated with Microsoft 365 Roadmap ID 518287. [When this will happen:] General Availability (Worldwide): We will begin rolling out in late May 2026 and expect to complete by mid-June 2026 (previously late May). General Availability (GCC): We will begin rolling out in mid-June 2026 (previously early June) and expect to complete by late June 2026. |
| 2026-05-28 | MC Last Updated | 05/21/2026 22:28:39 | 2026-05-27T19:00:54Z |
| 2026-05-28 | MC Summary | New Outlook for Windows supports LDAP directories for S/MIME certificate lookup, enabling secure encrypted email with external partners. Admins configure LDAP via Exchange Online PowerShell; users add directories in Outlook settings. Rollout starts late May 2026 worldwide, early June in GCC. Feature enabled by default, no authentication supported. | New Outlook for Windows will support LDAP directories for S/MIME certificate lookup, enabling secure encrypted email with external partners. Rollout begins late May 2026 worldwide, mid-June in GCC. Admins configure LDAP via Exchange Online PowerShell; users add directories in Outlook settings. LDAP must not require authentication. |
| 2026-05-22 | MC MessageTagNames | User impact, Admin impact | Updated message, User impact, Admin impact |
| 2026-05-22 | MC Summary | New Outlook for Windows will support LDAP directories for S/MIME certificate lookup starting late May 2026, enabling admins and users to configure LDAP for finding recipients’ public encryption certificates when sending encrypted emails. LDAP endpoints must not require authentication. This benefits organizations collaborating with external partners. | New Outlook for Windows supports LDAP directories for S/MIME certificate lookup, enabling secure encrypted email with external partners. Admins configure LDAP via Exchange Online PowerShell; users add directories in Outlook settings. Rollout starts late May 2026 worldwide, early June in GCC. Feature enabled by default, no authentication supported. |
| 2026-05-22 | MC Last Updated | 05/14/2026 22:15:13 | 2026-05-21T22:28:39Z |
| 2026-05-22 | MC Messages | [Introduction]
New Outlook for Windows now supports Lightweight Directory Access Protocol (LDAP) directories for S/MIME certificate lookup. This enables tenants to configure LDAP directories for their organization as well as enabling users to configure LDAP directories themselves. Once configured, users can find recipients' public encryption certificates from the directories when sending encrypted email, improving secure collaboration with external partners. This is especially valuable for tenants who collaborate with external partners and rely on public/partner LDAP directories to store public S/MIME certificates of users. This message is associated with Microsoft 365 Roadmap ID 518287. [When this will happen:] General Availability (Worldwide): We will begin rolling out in late May 2026 and expect to complete by late May 2026. General Availability (GCC): We will begin rolling out in early June 2026 and expect to complete by late June 2026. | Updated May 21, 2026: We have updated the content. Thank you for your patience.
[Introduction] New Outlook for Windows now supports Lightweight Directory Access Protocol (LDAP) directories for S/MIME certificate lookup. This enables tenants to configure LDAP directories for their organization as well as enabling users to configure LDAP directories themselves. Once configured, users can find recipients' public encryption certificates from the directories when sending encrypted email, improving secure collaboration with external partners. This is especially valuable for tenants who collaborate with external partners and rely on public/partner LDAP directories to store public S/MIME certificates of users. This message is associated with Microsoft 365 Roadmap ID 518287. [When this will happen:] General Availability (Worldwide): We will begin rolling out in late May 2026 and expect to complete by late May 2026. General Availability (GCC): We will begin rolling out in early June 2026 and expect to complete by late June 2026. |
| 2026-05-22 | MC Title | New Outlook for Windows: LDAP support for S/MIME certificate lookup | (Updated) New Outlook for Windows: LDAP support for S/MIME certificate lookup |
| 2026-05-22 | MC How Affect | Who is affected:
Organizations that use S/MIME encryption with external recipients whose public certificates are hosted in third-party LDAP directories Admins managing Exchange Online What will happen: Admins can configure LDAP directories using Exchange Online PowerShell. Users can add LDAP directories in Settings > Mail > S/MIME in new Outlook. When composing an S/MIME encrypted email, users can select recipients from the LDAP directory via the To field. LDAP endpoints must not require authentication, as authentication is not currently supported. Screenshot: "Add LDAP directory" option in Settings > Mail > S/MIME and LDAP recipient picker in the To field during message composition: Feature is enabled by default once available. No impact to: Classic Outlook for Windows users Organizations not using LDAP for S/MIME certificate discovery | Who is affected:
Organizations that use S/MIME encryption with external recipients whose public certificates are hosted in third-party LDAP directories Admins managing Exchange Online What will happen: Admins can configure LDAP directories using Exchange Online PowerShell. Users can add LDAP directories in Settings > Mail > S/MIME in new Outlook. When composing an S/MIME encrypted email, users can select recipients from the LDAP directory via the To field. This will directly enable Outlook to retrieve the certificate from the selected LDAP directory. If users add a recipient directly to the 'To list', Outlook will scan all available certificate sources, including the configured LDAP directories. LDAP endpoints must not require authentication, as authentication is not currently supported. Screenshot: "Add LDAP directory" option in Settings > Mail > S/MIME and LDAP recipient picker in the To field during message composition: Feature is enabled by default once available. No impact to: Classic Outlook for Windows users Organizations not using LDAP for S/MIME certificate discovery |
Last updated 3 weeks ago ago
