By default, Microsoft Outlook 2010 and Microsoft Outlook 2013 archive different items based on the item type, as follows:
Email message: The received date or the last modified date and time, whichever is later.
Calendar item: The last modified date and time or the actual date that an appointment, event, or meeting is scheduled for, whichever is later.
Task: The completion date or the last modified date and time, whichever is later. Tasks that are not marked as completed are not archived. Tasks that are assigned to other users are archived only if the status is completed.
Note: The last modified date and time.
Journal entry: The date when the journal entry is created or the last modified date and time, whichever is later.
Contact: Not archived.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
For Outlook 2010, the ArchiveIgnoreLastModifiedTime registry setting was introduced with the Microsoft Outlook 2010 hotfix package dated April 26, 2011 (KB2516474).
2516474 Description of the Outlook 2010 hotfix package (outlook-x-none): April 26, 2011
To create the ArchiveIgnoreLastModifiedTime registry value, follow these steps:
Click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then click the following registry subkey: