The premier on Tuesday met with his cabinet members, who pledged to push ahead quickly with structural reform.
Koizumi called the election after dissidents within his Liberal Democratic Party (LDP) defeated his effort to break up the post office, which is effectively the world's biggest financial institution with $3 billion in savings and insurance assets.
Ministers pledged to press ahead with that and other reforms, although local media said that the actual privatisation of the post office would be delayed by six months because of the election.
"Whether to privatise the post was the biggest issue in this election," said Heizo Takenaka, minister for economic and fiscal policy and postal reform.
"We've received strong encouragement by voters to firmly implement postal privatisation and to continue reforms," he said after the cabinet meeting. "As the people's will is clear, I would like to accelerate reforms."
But Japanese media said Takenaka told Koizumi that the start of breaking up the massive post office would have to be delayed until October 2007 because of the initial rejection by parliament.
The postal privatisation bills are expected to brought before parliament again in early October, Jiji Press reported.
Koizumi's coalition won more than a two-thirds majority in the election, enough to override any rejection by the upper house, which cannot be dissolved and where the coalition holds a slim majority.
Although the government's exact agenda remains to be charted out, one newspaper survey suggests an overwhelming majority of lawmakers in the new lower house support revising the pacifist constitution.
In one of the most controversial potential reforms, a Mainichi Shimbun survey published Tuesday said that 402 of the 480 lawmakers in the new lower house back reform of the pacifist constitution.
Any revision of the constitution, which was imposed by the US after Japan's defeat in the second world war, would likely anger neighbouring countries invaded by Japan in the early 20th century.
A constitutional amendment requires a two-thirds majority in both houses.