protected function compareMail($actualMail, $expectedMail)
    {
        // Make sure there is the same number of actual and expected.
        $expectedCount = count($expectedMail);
        $this->assertMailCount($actualMail, $expectedCount);

        // For each row of expected mail, check the corresponding actual mail.
        // Make the comparison insensitive to the order mails were sent.
        $actualMail = $this->sortMail($actualMail);
        $expectedMail = $this->sortMail($expectedMail);
        foreach ($expectedMail as $index => $expectedMailItem) {
            // For each column of the expected, check the field of the actual mail.
            foreach ($expectedMailItem as $fieldName => $fieldValue) {
                $expectedField = [$fieldName => $fieldValue];
                $match = $this->matchesMail($actualMail[$index], $expectedField);
                if (!$match) {
                    throw new \Exception(sprintf("The #%s mail did not have '%s' in its %s field. It had:\n'%s'", $index, $fieldValue, $fieldName, mb_strimwidth($actualMail[$index][$fieldName], 0, 30, "...")));
                }
            }
        }
    }