Walkthrough: How we use Hailuo to categorize inbound sales emails, with prompt examples.

Let's be honest, most of the "AI-powered email workflow" posts you see are glorified demos using perfectly structured, fake data. They skip the messy reality of real business communication, where emails are a chaotic mix of broken HTML, forwarded threads, three different languages, and the occasional "pls call me" from a CEO. So when our team decided to trial Hailuo for categorizing inbound sales emails, we went in expecting the polished marketing claims to fall apart immediately. Surprisingly, the core function works, but the path to getting there is paved with caveats and vendor-specific quirks that nobody talks about.

Our primary goal was to sort incoming sales inquiries from a shared inbox into five categories: "Pricing Request," "Technical Pre-Sales," "Partnership Inquiry," "Existing Customer Issue," and "Off-Topic/Junk." The initial, naive prompt looked something like this: "Categorize the following email into one of these categories: [list]. Return only the category name." The failure rate was about 40%. Hailuo would get confused by emails that contained multiple intents, like a pricing request wrapped in a technical compatibility question, and it would often hallucinate categories not on our list. More critically, it would sometimes make a definitive call on a poorly written email that actually required a human "I don't know."

After a week of failures, we had to engineer the prompt to account for Hailuo's particular sensitivities and our own need for uncertainty signaling. The final, working prompt is far more verbose and instructs the model to play a very specific role.

You are an email triage specialist for a B2B software company. Your task is to analyze the inbound email and assign the SINGLE most appropriate primary category from the list below. You MUST follow these rules:
1. If the email's primary intent is unclear, or if it clearly fits multiple categories, output "UNCLEAR: [brief reason]".
2. If the email is clearly spam, an automated newsletter, or completely off-topic, output "OFF-TOPIC".
3. Only if you are highly confident should you output one of the predefined categories.
Categories: Pricing Request, Technical Pre-Sales, Partnership Inquiry, Existing Customer Issue.
Email: {{EMAIL_BODY}}

This prompt, while effective, highlights the first major pitfall: prompt engineering is now a core part of your system's "codebase." This isn't a set-and-forget config; it's a brittle piece of logic that will need maintenance as Hailuo's models update. The "UNCLEAR" output is crucial because it forces a human review loop for edge cases, which we then use as fine-tuning data. Speaking of fine-tuning, we explored that option and the cost-benefit analysis is murky at best. Hailuo's fine-tuning costs are opaque until you engage with sales, and the lock-in it creates is severe. You're not just tuning a model; you're tuning *their* model, making a future migration exponentially harder.

The workflow now runs, but we're staring down the barrel of ongoing costs that scale directly with email volume, a dependency on Hailuo's API uptime (which has had two notable outages in the last quarter), and the gnawing question of whether an open-source model, hosted internally with a simpler rule layer, would have achieved 80% of the result for a fixed cost. It works, but every month's invoice is a reminder that we've traded capital expense for a perpetual operational one that is entirely outside our control.

Just my two cents