If your organization has disabled image reloading in HTML email, you can work around this by using an exception in the Outlook Trust Center.
You get to the Trust Center by opening your Outlook and clicking on “File > Options > Trust Center > Trust Center Settings”
There you must allow images to be downloaded from websites in the Trusted Zone.
Add the entry "https://*.sosafe.de" to the list of trusted sites in Windows Internet Options.
Reset the Windows Internet options. Switch to the options under "Advanced"(1), click on "Reset"(2) and then make sure that the checkbox "Do not save encrypted pages to disk"(3) is not checked.
These settings in Outlook Trust Center and Internet Options must be made on the client side. Depending on the infrastructure setup in your organization, you can distribute this configuration using Windows Server Group Policy:
Under the item "Computer Configuration\Administrative Templates\Windows Components\Internet Explorer\Internet Control Panel\Security Page\List of Site to Zone Assignments" in the group policies, please set the value 2
for https://*.sosafe.com. This makes SoSafe a trusted site. If Outlook already allows downloading images from trusted sites, you are done.
Otherwise, you also need to set the DWORD key "JunkMailImportLists" to 1. You can find this in the registry, under the section "HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\1x.0\Outlook\Options\Mail".
1x.0 stands for the respective version. Office 2010 is 14.0, Office 2013 is 15.0, and Office 2016 & Office 2019 are 16.0.