Each service provider chooses to work with a different format. There is no standard and because of that, if you are coming to Nabble or leaving Nabble you may run into the problem of having to "translate" the information from one format to the other.
If the destination service provider isn't able to provide a way to convert our format to theirs, they are, at least, able to provide their format specifications.
Any average developer should be able to convert from one format to the other. That's usually not a hard task. Sometimes a bit time consuming but not hard.
Nabble staff. We never ask for passwords.