Most marketplaces give you an API for customer messages. Mirakl platforms do; connecting one is a matter of an API key. Amazon does not, at least not for the thing sellers actually need. The Selling Partner API lets you send a handful of pre-defined message types to a buyer. It does not let you read what buyers write to you.

What Amazon does instead is email. Every buyer message is delivered to the address registered on your seller account, from an anonymised sender such as abc123xyz@marketplace.amazon.de. Replying to that address routes your answer back through Amazon, which stores it in the thread, shows it to the buyer, and stops the 24-hour clock.

That design has an upside: anything that can receive and send email can handle Amazon messages. This is how a shared support inbox gets Amazon in without an API.

How a relay works

In Seller Central you set (or add) the email address that receives buyer messages. Instead of a personal mailbox, you point it at an address the helpdesk owns, for example amazon-yourshop-a1b2c3@in.yourhelpdesk.io.
Amazon delivers each buyer message there. The helpdesk parses it: the buyer’s anonymised address (the reply-to), the order number in the subject or body, the marketplace (.de, .fr, .es), and the message text stripped of Amazon’s wrapper.
It becomes a thread in the same queue as everything else, with the order reference and the marketplace attached, and with Amazon’s deadline on the clock.
When an agent replies, the helpdesk sends an email from your verified sending domain to the anonymised buyer address, with the original subject, in-reply-to headers intact. Amazon accepts it as your reply.

Nothing about this is a hack. It is the mechanism Amazon designed, used with a different inbox on your end.

What the relay must get right

A relay that merely forwards mail is not enough. Four details decide whether it works or quietly damages your account.

Verification before anything else. The relay address must prove it receives Amazon’s mail before the connection counts as live. Otherwise a typo in Seller Central means buyer messages vanish into nowhere while the helpdesk shows a calm, empty queue. The connection should stay “pending” until the first round trip succeeds, and the helpdesk should tell you when it does.

The reply must go back through Amazon. Reply from the wrong sender, to the buyer’s real address if you somehow have it, or without the thread headers, and Amazon does not see it. The buyer might, but the 24-hour clock keeps counting and the thread shows as unanswered. The helpdesk needs to send to the anonymised address, from an address Amazon has on file for your account, and keep the subject.

Delivery has to be tracked. Email fails silently. A relay that fires the message and forgets it will show “sent” for a reply that bounced. The sending service reports delivery, bounces and complaints; the helpdesk should attach that state to the message and shout when something failed, so an agent can resend before the deadline, not after a warning from Amazon.

Amazon’s content rules apply to your reply. Buyer-Seller Messaging has rules about what a message may contain: no links to external sites, no marketing, no requests for reviews in certain forms, no tracking pixels. A helpdesk that appends an HTML signature with your website link to every email will append it to Amazon replies too. The relay channel needs its own rendering: plain, factual, no promotional footer.

The 24-hour clock, again

Amazon measures whether you respond to buyer messages within 24 hours, and its clock does not pause for weekends. Because relayed messages carry their arrival time, the helpdesk can put them on the same “time left” sort as every other marketplace. A Sunday 22:00 message shows up at the top of Monday morning’s queue with thirteen hours left, which is exactly what you need to know.

Messages that do not require a response (Amazon marks some that way) should not count against you, and a good parser recognises them rather than making you click “done” on each.

Where the relay stops

Honesty about the limits:

No history import. The relay only sees messages from the moment you switch the address. Older threads stay in Seller Central.
Attachments are email attachments. They come through, but Amazon strips some types.
No order data. The relay tells you the order number. It does not tell you the order’s status, what was in it, or whether it was refunded. Those still come from Seller Central (or an order integration) until you connect one.
One address per seller account. Multiple marketplaces on one account arrive at one address, which is fine: the marketplace is in the message.

Is it worth it?

If Amazon is one of six channels and the person answering it is the same person answering Leroy Merlin, WhatsApp and the shop mailbox, then yes. The point of a support queue is that there is one of it. Amazon being the exception, answered in a separate tab on a separate clock, is how Amazon threads become the ones that go overdue.

The relay puts Amazon in the queue. The rules above keep it inside Amazon’s lines while it is there.