Truth is a property of propositions. In the simple case of propositonal logic this means that any proposition is either true or false.
Either it rains or it does not rain, at a fixed date and time at a fixed point of Manhattan.
The most widespread definition of a proposition being true is due to Tarski: A proposition is true if and only if the actual situation, which the proposition is about, is a matter of fact. The proposition
It rains in Manhattan at a fixed date and time and at a fixed point
is true if and only if it actually rains. Otherwise the proposition is false. Hence Tarski's truth definition compares a proposition with a real situation.
Because mathematics does not deal with reality - it is not a natural science like physics - one cannot apply Tarski's definition to mathematical statements.
Instead, one has two related, but different concepts:
A mathematical statement of an axiomatized theory is provable iff and only it derives by a logical conclusion, i.e. a syllogism, from the axioms of the theory.
A mathematical statement is true if and only if it holds in any model of the axioms.
Any provable statement is true. The converse holds in simple theories like propositional calculus. But it does not hold in more general mathematical theories.
Taking your question literally, the answer is NO: There exist false mathematical statements by trivial reasons, e.g. There is a maximal prime number is a false mathematical statement.
There exist mathematical statements, the truth of which is undecidable, e.g. the continuum hypothesis is undecidable within ZF set theory.
There exist true mathematical statements. They are true in all possible worlds where our logic is valid, which means necessarily true.