FYI
PMs will remain in your Outbox until the recipient reads them, then they go into the Sent folder.
That way you know when it's not been read yet... remember other members have to sleep, eat and shop etc, and can be in significantly different time-zones from you, so you cannot always expect an instant response...
Back to the issue...
In Context-menu > Properties > Security... for the selected 'Components' folder [and for the Plugins, Materials and Styles folders next...]
Edit & Apply
Set Read/Write permissions to FULL for everyone that you can.
Then use...
Advanced>Owner
Set the owner of the folder to be 'admin', also ensure the changes filter down to change all contents to match [there is a check-box].
Do not have it set for the folder you are changing to take its permissions from its containing folder [SketchUp~] as this will confuse things...
Also set 'SketchUp.exe' to 'always run as administrator' in Properties > Compatibility...