Canalla translates to "scoundrel" or "rogue." It's a colorful and somewhat old-fashioned insult that adds a lot of character to the lyrics.
In the song, the narrator is frustrated and feels mocked, asking, "¿Cómo serás tan canalla?" (How can you be such a scoundrel?). It's used to express a strong sense of betrayal or disbelief at someone's deceitful or mischievous behavior, making it a memorable and emotionally charged word.
This song follows a guy in a rough neighborhood who keeps waiting on a letter that never comes. He blames the postman, he blames the police who rough up his friend, he blames anyone but the truth.
It's not really about the mail. Holland is famous for legal cannabis, so "letters from Holland" is a wink at running out of weed. The joke carries the whole song: he's convinced the letters "smell too much like plants" to make it through customs, which is exactly why they never arrive.
It's a playful, streetwise story more interested in wordplay than in a serious plot. Melendi teams up with Funzo and Baby Loud here, keeping the delivery loose and conversational while the central joke does all the work.