At the onset of his tenure as patriarch, John exchanged letters with the archbishop Marutha of Tikrit concurrent with the Muslim conquest of Persia, which allowed Marutha to inform John of the persecution of Syriac non-Chalcedonians in the Sasanian Empire by the Nestorian archbishop Barsauma in the 5th century. Formerly, Syriac non-Chalcedonians in Iran had been prevented from corresponding with their coreligionists in the Roman Empire as they had been labelled as Roman sympathisers and spies by Nestorians.
Upon taking office, John exchanged letters with Archbishop Marutha of Tikrit simultaneously with the Muslim invasion of Persia, enabling Marutha to inform John about the persecution of Syriac non-Chalcedonians in the Sasanian Empire by Nestorian Archbishop Barsauma in the 5th century. Previously, Syriac non-Chalcedonians in Iran had been barred from communicating with their coreligionists in the Roman Empire due to being labelled as Roman sympathizers and spies by Nestorians.