I am currently in the process of writing a cover letter for an application for a PhD position. Upon proofreading it, my girlfriend, who has had training as a European secretary, told me that her English teacher instructed them not to use “Yours sincerely” as a valediction in such correspondence (such as a cover letter) anymore and use something like “Best regards” instead, stating that “Yours sincerely” is too formal and old-fashioned.
How accurate is this information?