The Letter of the Holy Office 1949 agrees with Jesus and St.Faustina Kowalski.

Fifth Day

 "Today bring to Me the Souls of those who have separated themselves from My  Church  and immerse them in the ocean of My mercy. During My bitter Passion they tore at My  Body and Heart, that is, My Church. As they  return to unity with the Church My wounds  heal and in this way they alleviate My  Passion."

Most Merciful Jesus, Goodness Itself, You do : not refuse light to those who seek it of : You. Receive into the abode of Your Most : Compassionate Heart the souls of those who  have separated themselves from Your Church. (Our Lord's original words here were heretics and schismatics-Divine Mercy online).

 Draw them by Your light into the unity of : the Church, and do not let them escape from the abode of Your Most Compassionate Heart;  but bring it about that they, too, come to  glorify the generosity of Your mercy. 

Eternal Father, turn Your merciful gaze upon  the souls of those who have separated  themselves from Your Son's Church, who have squandered Your blessings and misused Your graces by obstinately persisting in their  errors. Do not look upon their errors, but  upon the love of Your own Son and upon His  bitter Passion, which He underwent for their  sake, since they, too, are enclosed in His  Most Compassionate Heart. Bring it about : that they also may glorify Your great mercy : for endless ages. Amen. (Divine Mercy Novena)

According to Vatican Council II (Ad Gentes : 7) all need 'faith and baptism' for salvation. Protestants and Orthodox Christians do not  have Catholic Faith.

The Diary of St.Faustina Kowalski is in  agreement with Vatican Council II (AG 7),  the Catechism of the Catholic Church (846) and the dogma extra ecclesiam nulla salus.

The Letter of the Holy Office 1949 mentions 'the dogma', the 'infallible teaching.'

Here is the dogma.

Pope Eugene IV, Cantate Domino (1441): "The most Holy Roman Church firmly believes, professes and preaches that none of those existing outside the Catholic Church, not only pagans, but also Jews and heretics and schismatics, can have a share in life eternal; but that they will go into the "eternal fire which was prepared for the devil and his angels" (Matthew 25:41), unless before death they are joined with Her; and that so important is the unity of this ecclesiastical body that only those remaining within this unity can profit by the sacraments of the Church unto salvation, and they alone can receive an eternal recompense for their fasts, their almsgivings, their other works of Christian piety and the duties of a Christian soldier. No one, let his almsgiving be as great as it may, no one, even if he pour out his blood for the Name of Christ, can be saved, unless he remain within the bosom and the unity of the Catholic Church."- Wikipedia, extra ecclesiam nulla salus (emphasis added)

-Lionel Andrades