Unfortunately, at this time, there is no way to change Outlook profiles from cached mode (1 month retention) to online mode in the Outlook settings.
To configure the cache settings in Outlook (2016/365) in a WVD session you need to use Active Directory GPOs or local Group Policies.
To use local group policies follow these steps:
- Download the following ADMX in your environment: https://www.microsoft.com/en-us/download/details.aspx?id=49030
- Extract the files
- Copy the outlk16.admx file to %systemroot%\PolicyDefinitions\
- Based on the language folders you see in your WVD host copy the outlk16.adml file from the admx\xx-xx folder to the relative folder in %systemroot%\PolicyDefinitions\

- Open gpedit.msc
- Go to User Configuration > Administrative Templates > Microsoft Outlook 2016 > Account Settings > Exchange > Cached Exchange Mode.
- Set “Use Cached Exchange Mode for new and existing Outlook profiles” to Disabled