GTIIT Knowledge Base - How To Back Up Your GTIIT Email

If you want to back up the message folders locally (in addition to keeping them on the server), you can export the items to a .pst file that you can restore later as needed and use by importing via Outlook desktop Application.

Open your Outlook application then select File > Open & Export > Import/Export.
Select Export to a file, and then select Next.
Select Outlook Data File (.pst), and select Next.
Select the mail folder you want to back up and select Next.
If you want to backup everything in your mailbox, simply select the top item, in the below screenshot you need to select anne@contoso.com
Choose a location and name for your backup file, and then select Finish.
If you want to ensure no one has access to your files, enter and confirm a password, and then select OK.

The messages that you keep in a .pst file are no different from other messages. You can forward, reply, or search through the stored messages as you do with other messages.