What is the test for malicious intent in the context of an appeal against the findings of a finding of malicious intent?

The determination of this appeal, in my opinion, turns on the question of whether there was any extrinsic or intrinsic evidence that the respondents were motivated by malice in writing the letter which is complained of. There can be little doubt that if there is evidence proving that the statements complained of are false to the knowledge of the person who makes them, they are taken to have been made maliciously, but this statement must be read in the light of the language used by Lord Atkinson in Adam v. Ward [[1917] A.C. 309.], at p. 339, where he said: ... a person making a communication on a privileged occasion is not restricted to the use of such language merely as is reasonably necessary to protect the interest or discharge the duty which is the foundation of his privilege; but that, on the contrary, he will be protected, even though his language should be violent or excessively strong, if, having regard to all the circumstances of the case, he might have honestly and on reasonable grounds believed that what he wrote or said was true and necessary for the purpose of his vindication, though in fact it was not so.