ASD's Blueprint for Secure Cloud

User Mailbox Configuration

This section describes the design decisions associated with User Mailbox Configuration for system(s) built using ASD's Blueprint for Secure Cloud.

Estimated reading time: 2 minutes

User Mailboxes are Exchange Mailboxes that are associated with a user account. Usually one mailbox is associated to one user account.

User mailboxes can be configured to:

  • Allow or deny Internet Message Access Protocol (IMAP) and Post Office Protocol (POP) connections
  • Prevent deletion of mail
  • Control ActiveSync connections
  • Control mail size limits
  • Control use of mail archives

The above configurations can be completed on all new mailboxes using a Client Access Services (CAS) Mailbox Plan. A CAS Mailbox Plan is used to configure settings when a licence is assigned to a new user. If the licence is changed, the CAS Mailbox plan linked to that new licence is applied. CAS Mailbox plans will be inherited from the existing organisational plans.

In addition to the above mailbox configuration, by default, standard user accounts have access to Exchange Online via Exchange Online PowerShell. ASD guidance to disable unneeded features requires that this feature be disabled.

Security & Governance

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Do you have a suggestion on how the above page could be improved? Get in touch! ASD's Blueprint for Secure Cloud is an open source project, and we would love to get your input. Submit an issue on our GitHub, or send us an email at

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Acknowledgement of Country
We acknowledge the Traditional Owners and Custodians of Country throughout Australia and their continuing connections to land, sea and communities. We pay our respects to them, their cultures and their Elders; past, present and emerging. We also recognise Australia's First Peoples' enduring contribution to Australia's national security.

Authorised by the Australian Government, Canberra