Never presume or guess the gender of the addressee. In one instance, I Googled the name of an intended addressee and found that the person identified as transgender. Rather than ‘Mr’ or ‘Ms’, I simply used the recipient’s first name and surname.
As a traditionalist, I think that using ‘they’ as a gender-neutral singular pronoun is just a slack way of making your text inclusive, whether for marketing reasons or out of fear of being considered politically incorrect.
On a fine January day, during the women’s singles final of the Australian Open tennis tournament, there was an incident. This incident involved a line call, a corrected line call, a chair umpire…and a conspicuous grammatical error.