CONFIRM: @digitalcircuit's 2018-06-10 recommendation works to complete do-release-upgrade from 16.04.5 to 18.04.1, after addressing exim4 issue.
CONFIRM: @digitalcircuit's 2018-06-10 recommendation works to complete do-release-upgrade from 16.04.5 to 18.04.1, after addressing exim4 issue.