Most "AI email agent" demos run one model against one mailbox: every message that lands gets the same prompt, the same context, the same handler. That's fine for a toy. It falls apart the moment your inbox is actually doing several different jobs — a billing question, a security report, and a sales lead all arriving at support@yourcompany.com within the same minute, each wanting a different specialist.
The naive fix is to make the one agent smarter: a giant system prompt that classifies, then branches into sub-behaviors. You end up with a monolith that's hard to test, hard to rate-limit per concern, and impossible to scale independently.
Here's the thing most people miss: one mailbox can feed several agents if you route mail into per-specialty queues before the agent ever sees it. You don't need a smarter agent. You need a smarter inbox. With a Nylas Agent Account the triage splits along one clean line. When you can route by sender — who the mail is from — inbound Rules do it server-side, sorting mail into per-specialty folders before it even reaches the mailbox. When you need to route by subject or content, a Rule can't see that, so your own worker classifies the message after a message.created webhook fires and moves it. Either way, a different worker drains each folder. The billing agent only ever sees billing mail. The security agent only ever sees abuse reports. Clean separation, no central classifier to babysit.
