...

and "doveadm mailbox delete" doesn't like it.

Does anyone have the magic sauce needed to escape the - character?

An "escaping" that works at the *nix level (not necessarily with doveadm, but I would assume it works there too) is, e.g.,

rm -- -foo

i.e., double dashes to nullify the "-" option flag, followed by the filename.

That does work. Thanks.

Alan