Going Deep with Architecture of Mailbox Dumpster in Exchange Server

In this article, we are going to see about the architecture of mailbox dumpster in Exchange system.


The Recoverable Deleted items folder is called Mailbox Dumpster. This folder has many invisible subfolders. They are called as parts of dumpster. Every mailbox is divided into two subtrees, they are IPM Subtree and non-IPM subtree. IPM stands for Interpersonal Messaging. IPM Subtree contains the normal visible folder like Inbox, sent items, drafts etc., Mailbox dumpster and its folders are stored in non-IPM subtree.

Parts of Dumpster:

Dumpster In ExchangeThe latest version of  consists of 6 layers and each layer has its own purpose of saving the emails. Most of this layers are invisible. Some are directly accessible and others are accessed by eDiscovery and other methods. Parts of Dumpster are,

  1. Deletions
  2. Versions
  3. Purges
  4. Audits
  5. Discovery Hold( Exchange 2013 & above)
  6. Calendar Logging

Deletions: This is first layer of Dumpster or the first sub folder. When an email is hard deleted (User deleting the email using Shift + Delete key), then the emails are directly placed in this folder. Though this folder is invisible, user can access this folder through and option called Recoverable Deleted Items, End-user can see the basic information and restore the emails to original folders.

Versions: This is the second layer of the Dumpster. This folder is invisible and not accessible directly. Only administrators can access the emails which is inside the folder using eDiscovery search. This folder contains the emails that are marked with In-Place Hold. This folder holds all the original copy and the edited copy of the emails. Compliance features highly rely on this folder.

Purges: This is the third layer in the Dumpster. This folder holds all the emails that are enabled or Single Item Recovery or Litigation hold. These emails are hard deleted by user, but mailbox has saved it for the purpose of compliance since litigation hold is enabled. If litigation is not enabled, then the emails in this folder will be purged after the retention period. This folder is invisible and not directly accessible.

Audits: This is the forth layer in the dumpster. When Mailbox Audit logging is enabled for the mailbox, all the Audit reports and logs are saved in this folder.

In-Place eDiscovery And HoldDiscovery Hold: This was introduced from Exchange 2013 version onwards. When emails are placed under In-Place Hold through discovery search, then this folder saves the copy of those emails even after the email is hard deleted.

Calendar Logging: This subfolder holds all the changes that occur in the Calendar of that mailboxes. This folder is not visible or accessible to the users.

All the above things are done by an agent called Mailbox Folder Assistant (MFA).

Benefits of Dumpster:

  1. Exchange Search Indexer indexes the Recoverable deleted item folder as well. This allows eDiscovery and other searches to happen fast.
  2. Separate quota limit is assigned to Recoverable Deleted Items folder. So this will not disturb the mailbox quota, users can access their complete mailbox quota.
  3. This prevents the data from being purged by exchange systems. Compliance will be healthy.


Dumpster has good amount of quota limit. The warning limit (soft limit) is 20GB and Hard limit of 30GB. This allows more space for the deleted items. When all these option fails, we still have an option OST 2 PST file Recovery.

Author Introduction: 

Sophia Mao is a data recovery expert in DataNumen, Inc., which is the world leader in data recovery technologies, including repair pst email error and word recovery software products. For more information visit www.datanumen.com

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