message-page {
    background: white;
    display: block;
    margin: 0 auto;
    margin-bottom: 0.5cm;
    box-shadow: 0 1px 5px rgba(0, 0, 0, 0.15);
    padding: 2.54cm;
}

    message-page[size="A4"] {
        width: 21cm;
        height: 29.7cm;
    }

        message-page[size="A4"][layout="landscape"] {
            width: 29.7cm;
            height: 21cm;
        }

    message-page[size="A3"] {
        width: 29.7cm;
        height: 42cm;
    }

        message-page[size="A3"][layout="landscape"] {
            width: 42cm;
            height: 29.7cm;
        }

    message-page[size="A5"] {
        width: 14.8cm;
        height: 21cm;
    }

        message-page[size="A5"][layout="landscape"] {
            width: 21cm;
            height: 14.8cm;
        }