What do I need to do, to let email be stored in this folder?

I asked Aquamail to save attachments on my SD card, but it had permissions issues. The info on the folder is below.

  • Aquamail error message:
    enter image description here

  • Folder info/permissions in FX:
    enter image description here

I understand that ideally, I should let Aquamail use the folder but not make it world-RW, which I guess means either giving Aquamail some permission, or adding it to some permissions group, but beyond that I’m not clear what the exact solution is. My phone is running LineageOS 15.1.

What is the correct way to fix this?