There is really no "official" teaching on this within Orthodoxy. Of course Orthodoxy is less inclined to declare things "official" dogma or teaching than some Western confessions are so that is not really that big of a problem. You'll find a great many doctrines we hold are not "dogmatic" teachings, in the sense that say Roman Catholics would use the term. However, even though there is no "official" teaching, the majority concensus seems to be that indeed people who are not in the Church, or not Christian may be "saved"...there is certainly no doctrine that I've ever read that follows the line of thought of some Baptists in the America that "even people who have never heard of Christ are doomed to hell"....if there was or is an Orthodox theologian who ever wrote or said something like that they are a lone voice amidst the vast Tradition of the fathers, saints, and theologians both ancient and modern who say the opposite.
There are many, many analogies that have been used over the centuries for the Church, but all seem to come with a possibility that those outside the Church most certainly can be saved. (especially people who have not heard the Gospel) A few thoughts like this would be something like, "We know where the Church is, we don't know where it isn't" . . .. "the Church is the Ark of Salvation and thus the safest way of crossing the tempest, but that doesn't mean someone else might not build a small row boat and make it across the sea too, it's just a lot harder in a row boat" . . . there are plenty of little sayings like that and many I've long since forgotten. But they all seem to follow Paul's idea in Romans that people will be judged by the light that they have been given. God is NOT unjust, and God is not cruel or unfair, and so I don't see God judging people for something they have no knowledge of. But as Paul says, the Creation itself preaches the Gospel, and declares God's glory, and so there is in some sense a "knowledge" that people have of God.
As for other religions, well, even many of the Church fathers talked about the ancient Pagan religions containing quite a bit of Truth, (though some fathers were totally against Paganism as being "evil" or of the devil, many were not and saw much good and Truth in them, though not the fullness of Truth, but rather as signposts pointing to the ultimate Truth which is Christ.
People who study non Christian religions, will find that they do contain Truth IMO, yes, some more than others for sure, but I don't think any historical religion is completely void of sign posts pointing to Christ. I remember listening to a lecture about the Orthodox mission to Alaska, and how many times when Natives would listen to the Missionaries they'd say something to the effect, "wow we already believe a lot of this, but now we perceive what we believed was "pointing" to a more ultimate Truth...can we be baptized?" (I paraphrase of course, but you get the idea)
Now before someone says, "well if everyone can be saved anyways, why preach to them at all"...and my answer is that "getting to heaven" is not the only goal of being a Christian. I don't think Christianity can be dumbed down to simply "going to heaven when you die" type of stuff. (forget that that's not really proper theology to begin with...because there will be an ultimate Resurrection and Restoration that "going to heaven" completely leaves out) But there is a lot more to Salvation than just going to heaven, or making sure we're part of the "in" group at Resurrection day. Salvation in Christ is more than just a ticket to eternal bliss, but as Christ said, He came to give life and LIFE more abundantly. There is something within Christianity, and within Orthodoxy in particular that I don't think can be acheived outside the Church. These are aspects of the Christian life like the empowering of the Holy Spirit to walk in the Spirit, to live in the Spirit, to live in the present reality that the Kingdom of God has come on earth, and yet that it is not fully "realized"...only inaugurated. The Gospel is "good news", but what is the good news? Merely a "ticket to heaven"? I think that's just too narrow of a view...the good news is all encompassing, a new way of seeing the world in Christ, that I personally think can only be realized in it's fullest within the Church. And so to me, that is the ultimate reason of preaching the Gospel even if one is practically a universalist (which I'm not and is not the Orthodox position) but even if it were, there is a whole lot more to being a Christian than just that "ticket to heaven" that certain Fundamentalists seem to narrow the Gospel down to. I want the LIFE in Christ....the hope, the love, that the saints and martyrs expressed...(not that I want to be martyred of course I'm far to weak for that). However I only type this because I'm sure someone would have asked the question "why preach at all if non Christians can be saved"...and this is my answer, although perhaps it doesn't make much sense...lol!
As for the idea of "mere" Salvation, ie: "going to heaven/being a part of the Resurrection unto life"....well, Christ as God, and King and Judge can save whoever He wants to save, and condemn whoever He wants to condemn. If this means saving every Hindu on the planet and sending every Christian to hell, well, He's the ultimate Judge and He gets to do it. Even if it disagrees with our theology. Which is why the best advice IMO is the old saying, for us to worry about our own walk with Christ, and no anyone elses. I think that is the closest you'll ever come to an "official" position, because frankly we don't know. And I think that's how it's meant to be.