Cicero to Tiro, written from Actium on the evening of the seventh day before the Ides of November — 7 November 50 BC — the same day as 16.4 and 16.5, but from the far side of the gulf, after the day’s crossing from Leucas. The salutation is the joint household one again: Tullius et Cicero et Q. Q. Tironi s. p. d. — “Tullius and Cicero and the two Quintuses send much greeting to Tiro.”

Cicero is candid about why he is writing for the third time in a day: he found a courier and did not want to waste him (magis instituti mei tenendi causa, quia nactus eram cui darem, quam quo haberem quid scriberem). The substance is the same as 16.4 and 16.5 in compressed form — love-as-care, the long list of Tiro’s services with one more to add: think not only about your health but about your voyage. The cluster’s two great anxieties, illness and the sailing season, finally sit together in one sentence. The closing imperative is doubled, cura, cura te, mi Tiro, and the formula again is etiam atque etiam vale.