I spotted some apparently broken info cross referencs in mh-e
defgroups,

        * mh-e/mh-customize.el (mh-folder-selection, mh-inc, mh-letter,
        mh-scan-line-formats): Corrections to custom-manual links.

I'm not certain about the mh-folder-selection change (the first in the
diff), but putting it to "Customizing Organizing" can't be too far
off, that node describes mh-default-folder-for-message-function which
is the first in the group.

Other defgroups referring to apparently non-existant nodes in the
manual are

  Symbol `mh-speed-faces' (in nil): cannot goto node: (mh-e)Speedbar
  Symbol `mh-junk' (in nil): cannot goto node: (mh-e)Junk
  Symbol `mh-alias' (in nil): cannot goto node: (mh-e)Aliases
  Symbol `mh-speed' (in nil): cannot goto node: (mh-e)Speedbar
  Symbol `mh-identity' (in mh-identity): cannot goto node: (mh-e)Identities
  Symbol `mh-toolbar' (in nil): cannot goto node: (mh-e)Toolbar

But none of these seem to have anything at all in the manual.