It is not a good idea to keep all the emails you send us saved in the Outlook, especially if in any of them there is valuable and important information, because at any given time, either by mistake when deleting it unintentionally, or accidentally by the attack of some spyware, all that information could be lost.
Therefore the best thing you can do is extract those files and convert them to other formats to read them more comfortably, apart from protecting them better, and that is what you can do with OutlookSpiller, which allows you to extract the emails from Outlook and pass it to the following formats : EML, MSG, TXT, HTML or even TNEF.
For the correct operation of Outlook Spiller you need to have previously installed the NET Framework 1.1 or higher.
You can free download OutlookSpiller 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.