The arrival of the owls carrying mail from home is one of the highlights of life at Hogwarts. Such was the scene one morning at Hogwarts, when Neville Longbottom received a gift from his grandmother (Book 1, Chapter 9). At the same time as Neville received his mail, Draco Malfoy also received mail carried by his eagle owl. Unless you're a reader of the Vietnamese version, of course, in which case you'll find that Malfoy's mail is carried by none other than an eagle (có)!
Could the translator, in her haste to complete the translation, have mistaken 'eagle owl' for 'eagle'? This is not beyond the realms of possibility given that the Vietnamese translation is not very strong on the names of types of owls (see The translation of 'owl' in Harry Potter).
On the other hand, the transformation of Malfoy's owl into an eagle could be a deliberate touch. Perhaps the translator consciously decided that an eagle would be more appropriate than a humble owl to carry mail for a predatory, arrogant person like Malfoy.