The Orthodox faith regarding this issue is thus:
There is no eclesiastical grace outside the Church. You can find healings, miracles, in sum, God does love everybody even those outside the Church and obviously listens to those who call upon Him, upon the Son, the Holy Spirit and likewise do the saints, the Theotokos above all. The love of God is not an exclusive club.
Said that "love of God" and "action of the Holy Spirit" does not equate "Church". Church is the Body of Christ, physical and spiritual. Like any body, it has pretty much defined limits - if anyone shows a person whose body "we know where it is, but we don't know where it isn't" than we can both start thinking about applying this reference to the Church *and* we can call the quantic physicists because we will have found the so desired macroscopic ambiguity of sub-particles. But since the Church is compared to a body and not to an electron, it is still a very well delimited body. There may be fair disagreements if it is the Orthodox, the Romans or the Non-Chalcedonians, but surely not "I'm sure I'm in, but we may all be in , better not say that someone isn't" which explains away but explains nothing.
So the Church has a delimited body, and we do believe that this well-defined body is the confederation of national churches known as the Orthodox Church. Very well. The non-Orthodox churches may be communions of faith, some of its members may be better disciples than an Orthodox, but, there is no salvific grace in any of them. None at all. Which means that their sacraments are just beautiful, inspiring rites.
Why, then, different bishops receive people from different jurisdictions in different ways? That has *nothing* to do with the status of "validity" of their rites. It has to do with pastoral decision. The duty of the bishop is to facilitate entrance into the Church, not to prevent it. Many new converts are not mature enough in the faith to face the fact that, as pious as they may have been before, there was no salvific grace there. Most react with "then it was all useless!". Of course it wasn't useless, it helped bring the person into the Church. It also shaped and cultivated his personality to better adapt to the Church. But had them stopped there, there would be no salvific grace whatsoever. So, the rule is: they are all out of the house, and the duty of the bishop is to help them get in, even if it is through the window, the chimney a crack on the wall or whatever. It's full of wolves out there, you have to bring in as many as you can as fast you can. If, though, the bishop sees that this flexibility is being abused, he may resume the strictness of the admission and demand full baptism.
Now, the point that most people usually really want to know... if there is no salvific grace in their churches, then they are lost and damned forever? If a person dies as a Roman or Protestant is the person condemned to hell? Of course not. We see in Matthew 13:24-30 and Matthew 13:36-43. In fact all the parables in this chapter apply to the Church, because the Church is the Kingdom of Heaven on Earth. Everything said of the Kingdom applies to the Church. And what is it that we learn in these parables? That when the Last Judgment come, some who are in will be spilled out, and some who are out will be brought in. So, the Church is salvation itself, here, now, not in the future. But in this world and age, there are good seeds and tares in it. This is very easy to see. Likewise, when we look outside the church, we see lots of good seeds and also lots of tare. Last Judgment will put all the good seeds in the Church and all the tares out.
So, there is no salvation (and therefore sacraments) outside the Church, and yes we can know where the Church is now. We can also know who is in it and who is out. But, what we can't know is who will be kept in and who will be kept out, who will be spilled out and who will be brought in. Today good seeds and tares are mixed. After the Last Judgment they will be separated.
Therefore, if by salvation you mean the ultimate fate after the Last Judgment, there is no guarantee for anyone. If by salvation you mean the actual presence of the salvific energy of the Church, than it is exclusively in the Church that is One/Undivided, Holy, Catholic/Orthodox, Apostolic.