Fascinating inquiry. To determine whether an organism is classified as a mammal, it must possess several defining characteristics:

Warm-blooded: Ferengi are likely warm-blooded. Although Ferenginar, their homeworld, has a warm and humid climate suitable for cold-blooded creatures, Ferengi coexist in various environments alongside humans without any apparent temperature-related issues. This suggests that they can regulate their body temperature.

Hair growth: Yes, Ferengi can grow hair, particularly in their ears, as observed in older individuals despite being mostly bald.

Milk feeding: It is probable that Ferengi females possess mammary glands, indicating the ability to produce and provide milk for their young, implying lactation.

Live birth: Based on references to Ferengi pregnancy and the absence of any mention of egg-laying, it can be inferred that Ferengi, like other humanoid species, give birth to live young.

Considering these factors, it is highly likely that Ferengi meet the criteria for being classified as mammals.