> PgDown in Mutt goes to next email when I reach the bottom of the current one.

    set pager_stop=yes

> Or deleting email keeps it displayed in the list ... but doesn't allow navigating to it to undelete

    -bind index n next-undeleted
    -bind index p previous-undeleted
    -bind pager n next-undeleted
    -bind pager p previous-undeleted
    +bind index n next-entry
    +bind index p previous-entry
    +bind pager n next-entry
    +bind pager p previous-entry

(Not sure why these aren't the defaults. They seem much more usable than the defaults!)