Current behavior (by design): In Dynamics 365, the Mailbox setting "Delete Emails after Processing" cannot be changed to "Yes" from the Mailbox UI screen. This field is read-only by design, even when:

• Creating a new mailbox record (the option is not available at creation time)
• Setting the mailbox to Inactive → Active again
• Editing the mailbox through the standard form

Currently, the only workaround is to create a Business Rule on the Mailbox table to force-update the field value, which is not intuitive for end users and administrators.

Requested improvement: Please allow users (with appropriate privileges) to directly toggle the "Delete Emails after Processing" field between Yes / No from the Mailbox configuration UI, without requiring workarounds such as Business Rules or backend modifications.

Business value / Why it matters:

• Many customers integrate Exchange Online with Dynamics 365 and want emails to be removed from Exchange Online once synced to Dynamics 365 (for storage, compliance, or data governance reasons).
• Currently, admins must rely on workarounds (Business Rules) which:
• Are not discoverable for typical admins
• Increase configuration complexity
• Are difficult to maintain and troubleshoot
• Making this setting directly editable in the UI would significantly improve the usability and administrative experience of Dynamics 365.

Customer impact: This feedback has been raised by enterprise customers in Japan (e.g., OKI Software) and would benefit all organizations using Server-Side Synchronization with Exchange Online.