Most transactional email setups end at "send." You wire up SendGrid or Postmark, point your auth flow at it, and your magic links, OTPs, receipts, and "is this you?" alerts go out the door from no-reply@yourcompany.com. It works. The user gets the code. The flow completes.
Then a user hits Reply.
Maybe they're confused by the OTP. Maybe they want to dispute a charge on a receipt. Maybe they're answering the "is this you?" security alert with "no, that wasn't me." Whatever they typed, it just hit a black hole. no-reply@ is, by design, an address nobody reads — and on most ESP setups it isn't even a real mailbox, so the reply either bounces or vanishes into a relay. The message you sent invited a human response, and you built it on a channel that physically cannot receive one.
That's the gap I want to close here. For pure one-way blasts — a marketing newsletter, a "your export is ready" ping — a one-way sender is genuinely fine, and I'll say so again at the end. But auth and transactional mail is different. A surprising amount of it is implicitly a conversation opener, and the moment you want an agent (or a human) on the other end of the reply, the no-reply model falls apart.
The fix is to send that same mail from a Nylas Agent Account: a real, grant-backed mailbox that can both send and receive. I work on the Nylas CLI, so the terminal commands below are the exact ones I reach for — and every one of them is paired with the raw HTTP call so you can see what's actually on the wire.
