try this
private void button1_Click(object sender, EventArgs e)
{
List<string> lstCheckedEmails = new List<string>();
foreach (var item in checkedListBox1.CheckedItems)
{
string email = item.ToString();
lstCheckedEmails.Add(email);
}
foreach (DataGridViewRow row in dataGridView1.Rows)
{
string email = row.Cells["EmailColumnName"].ToString();
if (lstCheckedEmails.Contains(email)) {
string pass = row.Cells["PasswordColumnName"].ToString();
}
}
}