You can archive your emails by using Outlook Data File (.PST) (aka Personal Data File) in Outlook. First of all, you need to create a "Outlook Data File". Then you can copy the email from any folder of your mailbox to the "Outlook Data File".

For Outlook 2019/2016:

Create Outlook Data File (PST):

  • From the Home tab, click New Items -> More Items -> Outlook Data File....

  • Specify whether the archive to store (e.g. D:\email_archive). And provide a file name for it. If you want to set a open password, remember to tick the option Add Optional Password. Then click "OK

  • The "Outlook data file" will be displayed on the left panel.
Change the Outlook data File display name or password
  • Right click the Outlook Data File and choose Data File Properties.

  • Choose Advanced.

  • Then enter the display name in Name box. If you want to modify the open password, click the Change Password... button to set your open password.

Note: The Outlook Data File can only be opened using Microsoft Outlook.