Office 365 Shared Mailboxes: Simplifying S/MIME Certificate Management

Office 365 Shared Mailboxes: Simplifying S/MIME Certificate Management
14 Jun ‘24

In a previous blog, we delved into KeyTalk’s support for Entra ID and Exchange Online, specifically focusing on the issuance of S/MIME certificates and private keys for shared mailboxes. Now, with several months of operational experience, we have refined our approach to address previously unforeseen use-cases, enhancing our service to better meet the needs of IT administrators.

The Challenge: Managing Dynamic Shared Mailbox Memberships

One of the most significant challenges faced by IT administrators is the dynamic nature of shared mailbox memberships in Office 365. Employees take on new roles, new users are added, and others leave or change their names. This constant flux requires continuous updates to ensure that the right individuals have access to the necessary secure email communications.

For KeyTalk, this means regularly checking with Entra ID or Exchange Online to stay updated on these changes. Our solution now includes periodic validations to ensure that S/MIME certificates are up-to-date and appropriately distributed. This automation not only saves time but also mitigates the risk of unauthorized access.

The Complexity of Scale

While periodic checks on Entra ID and Exchange Online might seem straightforward, the scale can be overwhelming. With potentially tens of thousands of users, each linked to tens or hundreds of shared mailboxes, the task becomes monumental. Our team has enhanced the KeyTalk agent software to monitor the availability of shared mailbox S/MIME certificates and manage membership changes efficiently.

Intune and Server Resource Optimization

Our interaction with Intune also required significant updates due to its connection limitations. Additionally, querying Exchange Online and Entra ID in our initial implementation put a considerable strain on server resources. We have since rethought our server resource management, optimizing it to handle the demands more effectively.

Operational excellence in S/MIME

Looking ahead, we are excited to extend our advanced shared mailbox S/MIME support to on-prem Active Directory and regular Exchange environments. This expansion aims to provide seamless and secure email communication across various platforms, ensuring that IT administrators can manage their infrastructure with greater ease and confidence.


Managing S/MIME certificates for shared mailboxes in Office 365 presents unique challenges for IT administrators. However, with KeyTalk’s ongoing improvements and innovative solutions, these challenges can be effectively addressed. By automating certificate issuance and updates, integrating seamlessly with Entra ID and Intune, and optimizing server resources, we ensure secure and efficient email communication across your organization.

Stay tuned for more updates as we continue to innovate and simplify secure email management. For more information, visit our website or contact our support team.

Interested after reading our blog? Contact us if you want to know more on our Secure Email Service or other S/MIME certificate automation related services.


The KeyTalk Team