The mailwatch plugin needs some icons provided by the xfce4-icon-theme Rodent.
However, if you use another icon theme, the icons are not found and so they are
However, other xfce apps (like the panel) install default icons in
/usr/share/icons/hicolor that serve als fallback if you choose another icon
theme. So they maybe don't fit into the theme, but they are here.
It would be good if the mailwatch plugin could do the same. For now, I just
Steps to Reproduce:
Looks like I fixed this a while ago but forgot to close the report. Whoops...