"Either there is no default mail client or the current mail client cannot fulfill the messaging requirements. please run Microsoft Outlook and set it as the default mail client"
Office365 Outlook is not being correctly detected by the DLO Agent, for support of PST files
1) In Windows, go to Start - Settings - Apps - Default Apps and ensure that Outlook is configured as the default Email application. Once this setting is changed, Exit and relaunch the DLO Desktop Agent.
2) If that does not resolve the issue, make the following changes in the Registry;
Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry is done prior to making any registry changes.