When I subscribe to a NG, then click on it to display recent messages, I get
a corresponding DBX file in the message folder. When I subsequently
unsubscribe that NG, the DBX file typically goes away. That is the behavior
I expect.

But in some instances, after unsubscribing, I am left with DBX files of
non-zero size. For example, m.p.e.worksheet.functions(1),
m.p.e.worksheet.functions(2), m.p.e.worksheet.functions and m.p.excel, where
"m.p.e" is microsoft.public.excel.

They persist even after I remove all NG accounts (leaving one mail account).

Why are those file left behind, whereas others are not?

Can I simply remove those files manually (i.e. right-click the icon and
delete)?

Presumably I should exit OE if/when I do that.

Is there a cleaner way to remove those orphaned(?) DBX files, like Tools
Options Maintenance Clean Up Now?

I tried Reset, to no avail.