Archiving - Minimum Retention Setting

This article provides information about the Minimum Retention Setting. 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 the:

• The minimum retention setting is set in days at the account level of your Mimecast service.
• The 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 your 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 Archiving - Minimum Retention Setting page for more details.

The Minimum Retention Setting Impact

Mimecast stores your organization's data in storage segments. These 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.

Your Minimum Retention Setting Finding

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

1. Log in to the Mimecast Administration Console.
2. Navigate to 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 on April 24 2015 with a Minimum Retention setting of 3653 days (10 years) would be retained indefinitely through April 24 2025.
• Policy: It is possible to retain email for less than your organization's minimum retention using either:
  • A combination of metadata and Email Security Cloud Gateway - Content Preservation Policy based on specific senders and / or recipients.
  • A Content Examination Policy that allows you to set the metadata and content preservation lifespan based on administrator-defined content in message components.

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.