"And how can one preach if he has not been sent?"
Good question.
St. Mark was sent to the Egyptians, and he founded upon his preaching the risen Lord our God Jesus Christ my Church, the Coptic Orthodox Church, which for centuries afterwards was the Church of all the Christians in Egypt. (Only later did the Greeks split off according to the minority position in Egypt, with their acceptance of Chalcedon which the native Egyptian bishops and a good number of others did not accept.)
St. Peter and St. Paul were sent to Antioch, where they founded those churches who trace their origins back to Antioch (the Syriac Orthodox Church, the Antiochian Greek Orthodox, the Syriac Maronites and other Syriac Catholics, except for the Chaldeans and the Syro-Malabar, who both have their origins in the preaching of St. Thaddeus in Mesopotamia, as the Nestorians also do).
St. Thaddeus (Addai in Syriac) was sent to Mesopotamia, where together with one Mar Mari (I'm not sure if he corresponds to any saint known in the West or not), he founded the Church in that country, which split off in many different directions following Ephesus in 431, with the bulk adhering to the Christology of Nestorius (those who make up the "Church of the East", sometimes also known as the Persian Church, or according to their detractors like me, the Nestorians), and a minority adhering to the Orthodox position (the Syriac Orthodox, historically very evident in the area that is now known as Tikrit -- infamous as the birthplace of Saddam Hussein -- with 8th and 9th century theologians like Abu Rai'ta al-Takriti, Quriyaqos of Tagrit, and Anthony of Tagrit being some of the finest Syrian theologians of the era; Abu Rai'ta wrote a famous defense of Christianity addressed to the new Muslims in his
Risala in the 9th century), as it remains today in that country. The only difference is there is now (since the 16th century) also Syriac and Chaldean Catholics, born of later schisms from these larger bodies (the Syriac Catholics from the Syriac Orthodox, and the Chaldeans from the Church of the East).
St. Thomas was sent to India, where he established the Church in 52 AD. Now there are many different Christian sects, but historically the main ones have been the Syriac Orthodox, Malankara Orthodox (essentially the same as the Syriac Orthodox, but autocephalous from the mother Church in the Middle East), and the Church of the East (very few in number these days, but very important historically). All of the Catholics -- most of whom are now Latinized in their worship following historical events like the Synod of Diamper (1599) -- descend from one or another of these groups: the Syro-Malabar from the CoE, the Syro-Malankara from the Malankara Orthodox, etc. There are also Protestants in the Mar Thoma Church (essentially Anglicanism with a Syriac veneer; very unique in that regard!), the Church of North India (Anglicanism as well, but this time without the Syriac because it's North India, rather than South India where Syriac Christianity already predominated by the time Anglican missionaries got there), etc.
St. Bartholomew and St. Thaddeus went to Armenia, where they established the Armenian Apostolic Church there.
The Ethiopian Orthodox Tewahedo Church in one way or another dates back to the first century, as Ethiopians were early recipients of the Gospel (as attested to in the Bible itself, as we know), but in terms of their establishment as a Church date to the beginning of the fourth century with the acceptance of Christianity by King 'Ezana, who was tutored in his youth by the Syro-Greek Christian Frumentius, who became the country's first bishop. (Bishops were since that time sent from Egypt, as Egypt is recognized as the first Christian Church of Africa, hence when they needed bishops they requested them of Egypt, rather than another place.)
The Syriac Christian tradition is basically as old as Christianity itself, so it was less a matter of specific missionaries being sent to them (though there is the tradition of St. Thaddeus delivering the
icon of Christ to King Abgar V, the first Christian king in the world, King of Osroene in Upper Mesopotamia in the first century AD), and more that they were just the people who were around (together with the Greeks, Arabs, and others specifically mentioned in the Scriptures) when the Gospel was originally being preached. Their keeping of the earliest extant anaphora (that of St. James, the Brother of the Lord) as their basic anaphora -- as in the Syriac Orthodox tradition -- attests to this. It is known that our Lord and his apostles spoke Aramaic, which is the parent language of the Classical Syriac that is still used in the liturgy, and of the modern Neo-Aramaic languages still spoken by many Syriac Orthodox (Suryoyo -- in Iraq, Turkey, Syria, etc.), Chaldeans (in Iraq and Iran), Nestorians (in Iraq and Iran), and others.
I think that covers just about everyone. The Greek traditions should be obvious as Greek was the overarching
superstratum culture of the entire East at the time, so of course the early dates and apostolic foundations of the churches of Greece, Cyprus, and the other places mentioned in the Bible itself is not really debatable. We can say similarly about the origins of Rome, however disputed its place as a See may be as a result of subsequent events (*cough*).
So what is all this about not being sent?
(I am blessed that their opinion about that doesn't matter in the grand scheme of things.)
