Archiving - Understanding Data Retention

Mimecast's Maximum Retention settings determine the length of time it will retain your organization's archives, which is critical to its integrity. Maximum Retention settings are set in days, at the account level of your Mimecast service. The amount of time set on your account should match the time outlined in your agreement. 

It is important to validate your maximum retention setting. To eliminate human error and provide a high level of data assurance for your organization, an administrator must initially validate the Maximum Retention setting. Every time the Maximum Retention changes validation will be requested again. Read the Validate Maximum Retention article to learn more about this process and how to confirm your Maximum Retention.

The Maximum 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 Maximum Retention setting directly impacts your organization's storage segments. Once a storage segment's end date passes the age as defined in the Maximum Retention setting, it will expire and become eligible to be purged.

If a storage segment contains emails that have been placed on Legal Hold, that segment will still expire but the items that have the Legal Hold applied will remain available for administrative searches until the time period defined for the Legal Hold has passed.

We purge an expired segment after 90 days unless one or more active Legal Holds have been configured on your account. Consequently, it is critical to your organization's contractual agreement with Mimecast that the Maximum Retention setting is accurately validated by a suitable administrator.

Finding Your Maximum Retention Setting

Maximum Retention settings are defined in the Administration Console. To view the Settings for your account:

1. Log in to the Mimecast Administration Console.
2. Navigate to Account | Account Settings.
3. The setting is shown in the Maximum Retention (Days) field.

How Email Retention is Calculated

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 Maximum Retention setting for your service. For example, an email received on April 24 2015 with a Maximum Retention setting of 3653 days (10 years) would be retained until April 24 2025.
• Policy: It is possible to retain email for less than your organization's Maximum Retention using either:
  • A combination of Metadata and Content Preservation Policies 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 on April 24 2015 with a Maximum Retention setting of 3653 days (10 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.

When using these policies, emails that do not match the specific sender and recipient values defined in the policy will be subject to the default Maximum Retention setting. Once an email has passed its expiry date it is no longer discoverable in the Mimecast archive.

Functionality That Impacts Message Retention

Some Mimecast functionality can impact an email's retention after its original expiry date has been calculated. These include:

•  A Retention Adjustment allows you to modify the original expiry date for emails in your organization's Mimecast Archive.
• 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 email's original expiry date. The expiry date of an email on legal hold cannot be changed by the Granular Retention Folders or Retention Adjustments features.

See Also...

• Maximum Retention Settings FAQ