Collection not able to concatenate

Hi I would like to concatenate the collection with a semicolon using string.join. However, I couldn’t concatenate with the semicolon , not too sure why?

we would recommend debugging the flow and with the usage of breakpoints inspecting the part result by using the different debug panels

Understanding the 6 Debugging Panels of UiPath in the easiest way possible! - News / Tutorials - UiPath Community Forum

maybe you can share with us the insights of the email List variable

can you upload the input file and xaml?