Firstly, the sentence is grammatically correct. It is a complex sentence where the main clause and the subordinate clause has been rearranged to for a conditional sentence. For example, you could express the same meaning through rearranging the clauses into 'We will inform you about it if this package is shipped out'.
We will inform you about it: main clause
If it is shipped out: subordinate clause
Moreover, the sentence 'If this package is shipped out, we will inform you about it' contains a possible condition and its probable result with the if clause written in passive voice but present tense present, while the main clause is written in the simple future tense. This means that it is a type 1 conditinoal sentence.
I hope that this helps!