Minimum Retention Settings: Technical Concepts

Document created by user.bx3iB36ab3 Employee on Apr 9, 2019Last modified by user.bx3iB36ab3 Employee on May 2, 2019
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Minimum retention settings are critical to the integrity of your Mimecast archive, as they control the minimum period Mimecast stores your organization's archived data. Consider that the:

  • Minimum retention setting is set in days at the account level of your Mimecast service.
  • Length of time set on your account should match the time outlined in your agreement when Compliance Protect is enabled.
  • Minimum retention cannot be decreased at any time.
To mitigate human error, and provide a high level of data assurance for you organization, the minimum retention setting must initially be validated by an administrator. Should the minimum retention setting need changing, validation must be requested again. This value cannot be decreased once set. See the Validating Your Minimum Retention Setting page for more details.

The Minimum Retention Setting Impact


Mimecast stores your organization's data in storage segments that can be viewed in the Administration Console via the Administration | Archive | Storage Segments menu item. Storage segments are allocated by date, and email data is stored in the segment that matches the sent date of the email. Depending on the profile of your organization's mail flow, these segments will either be allocated on a daily, weekly or monthly basis. The greater the volume of email your organization sends and receives, the shorter the length of the segment. The segment time period is defined by Mimecast, and is calculated to provide the optimal experience for your organization.


The minimum retention setting has a direct impact on your organization's storage segments. Once the end date of a storage segment has passed the age as defined in the minimum retention setting, the segment does not expire or become eligible to be purged. If a storage segment contains messages that have been placed on Legal Hold, that segment never expires but the items that have the Legal Hold applied remain available for administrative searches until the time period defined for the Legal Hold has passed.

If all policies, definitions, tasks, and retention adjustments that contain a value lower than the minimum retention value are not disabled or removed, the minimum retention does not take effect.

Minimum Retention SettingFinding Your Minimum Retention Setting


Minimum retention settings are defined in the Administration Console. To view your setting:

  1. Log on to the Administration Console.
  2. Click on the Administration toolbar menu item.
  3. Select the Account | Account Settings menu item. The minimum retention setting is displayed in the Minimum Retention (Days) field.

Calculating Email Retention


Email retention can be calculated in two ways, and is originally set at the point Mimecast first processes the email:

  • Default: By default the calculation is based on the Minimum Retention setting for your service. For example, an email received April 24 2015 with a Minimum Retention setting of 3653 days (10 years) would be retained indefinitely through April 24 2025.
  • Policy: It is not possible to retain email for less than your organization's minimum retention using either:


For example, the same email received April 24 2015 with a minimum retention setting of 2190 days (6 years) and subject to metadata and content preservation policies defined to retain email for 365 days (1 year) would be retained until April 24 2016 as defined by the administrator. With the minimum retention applied, these policies cannot be created due to the 365 day value being below the minimum retention setting of 2190 days. When using these policies, the value must be higher than the minimum retention value.


The Message Retention Impact


There are some Mimecast features that can impact a message's retention after its original expiry date has been calculated. They must also be disabled or finish running before compliance protect is enabled. These include:

  • The specified item was not found.his feature uses the Mimecast Synchronization Engine and administrator defined policies to adjust the retention of a message based on its folder location in the Exchange mailbox.
  • Retention Adjustments: A retention adjustment allows you to modify the original expiry date for messages in your organization's Mimecast archive.
  • Legal Hold: Messages placed on legal hold are retained for at least the duration that the legal hold is active, even if this is longer than the message's original expiry date. The expiry date of a message on legal hold cannot be changed by the granular retention folders or retention adjustments features.


With minimum retention active, you cannot create new managed folder tasks or retention adjustments if the day value is below the minimum retention value.


Frequently Asked Questions


Q:What happens if my organization fails to confirm the minimum retention setting?
A:This may result in Mimecast retaining your data incorrectly. Mimecast Account Managers will from time to time contact customers who have failed to confirm their minimum retention setting.
Q:What if no one within my organization is a member of a suitable Administrator Role?
A:Contact our Support Team to inform them that your organization requires a Super, Full or Partner Administrator account in order to validate the minimum retention of your account. They will respond with the appropriate procedure to follow. See the Understanding Administrator Roles page for more details.
Q:What if the password for an account that has a suitable Administrator Role has been forgotten?
A:Contact our Support Team stating which account requires a password reset and what administrator role it has. They will respond with the appropriate procedure to follow.
Q:Where can I see who has a suitable administrator role in my organization?
A:Select the Account | Roles menu item in the Administration Console to list your organization's administrator roles. Click on a role to see who the members of the role are.
Q:Will we have to go through this process every time there is a change to the minimum retention of our Mimecast account?
A:Yes. After the initial confirmation, Mimecast will seek further confirmation of the minimum retention setting after each update of this value. Minimum retention cannot be decreased from the original value but can be increased at any time.
Q:What if nobody within my organization knows what the minimum retention of our Mimecast account should be?
A:Contact your internal Legal and Compliance teams. They will assist you with your query.
Q:What if the current minimum retention is incorrect?
A:Contact our Support Team or your Mimecast Account Manager immediately. They ensure that the minimum retention gets updated after appropriate checks have been carried out.


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