Marketplaces and Classified Ads

In short. A selling address outlives the sale by years and ends up in lists you never agreed to. This is one of the few situations where a throwaway address fits almost perfectly, provided you keep it separate from your marketplace account.

What happens to a seller's address

You list a sofa. Four people write, one buys it, the sofa leaves. Your address now exists in four strangers' mailboxes permanently, and on many classified sites it was visible on the listing page itself for anyone to collect.

Collection is automated. Scrapers walk listing sites continuously, harvesting contact details into databases that get resold. The address you used for one piece of furniture becomes an entry in a list of "verified active sellers", which is worth more than a random address and gets traded accordingly.

The spam that follows is not the ordinary kind. It is aimed at people who have demonstrably sold something, which makes it more specific and more convincing.

What arrives, and what it is trying to do

Three patterns show up again and again in seller mailboxes.

The fake delivery service. A message claiming the buyer has paid through a courier's protected payment service, with a link to "confirm receipt" or "enter your card to receive funds". The site behind the link is a copy of a real courier's page. Money moves out, not in.

The fake payment notification. A message that looks like it comes from the marketplace, telling you the payment is held pending your confirmation. Same mechanism, different costume.

The verification link. No money mentioned at all. Just a request to confirm your listing, your account or your identity, leading to a login page that harvests your marketplace credentials. This one works because it asks for something plausible.

All three fall apart under a look at where the message actually came from, which takes about ten seconds and shows that it never passed through the courier or the marketplace it claims. All three also depend on reaching you by email, so all three become considerably harder if the address they reached you at stops existing when the sale does.

What we do to that mail before you see it, and what we do not

Since this page is mostly about mail written by strangers with a motive, it is fair to say exactly what happens to it on the way in.

Every message body is cleaned once, when it arrives rather than when you open it. Scripts, stylesheets, embedded frames and similar containers are removed together with everything inside them, so nothing runs and nothing leaks out as stray visible text. Inline styling is dropped entirely, which matters more than it sounds: styling is how a message paints a convincing fake panel over the page it is displayed in. Only ordinary web and mail links survive, so the tricks that hide executable content inside a link or an image never render. What is left is then displayed inside an isolated frame, and remote content in messages is not fetched by default, which is why the tracking pixels in marketplace spam mostly do not fire.

Now the honest half. A cleaned message is still a phishing message. The link to the fake courier page is an ordinary link to an ordinary web address and it works exactly as its author intended the moment you click it. Cleaning removes the ways a message can attack your browser. It does nothing about the ways a message can attack you, and on a marketplace the second is the whole problem.

The attachment that is supposed to be an invoice

Seller mail arrives with attachments, and a share of them are the point of the message rather than a courtesy.

Files with plainly executable extensions are never stored at all. The refusal list covers the obvious ones and the ones people forget: program files and installers, script files, shortcut files, disc images, mobile packages, registry and command files, roughly three dozen extensions in total. If a message arrives carrying one, the message still lands and the file simply is not there.

There are two size ceilings as well. A single attachment above five megabytes is skipped while the message itself still arrives, and a message above ten megabytes is dropped entirely and silently, without a failure notice going back to whoever sent it. Anything that is stored is served with a header that forces a download instead of a display, and labelled as a generic binary so a browser will not decide to open it helpfully.

The limit is the same shape as before. A document with a macro in it is still a document with a macro, and a legitimate looking invoice is still whatever you choose to do with it after it reaches your disk.

Why this scenario suits a throwaway address

Most bad outcomes with disposable addresses come from using one where recovery matters later. A private sale is the rare case where later genuinely does not exist: the deal closes in days, the item leaves, and nothing about it needs to be reachable next year.

The timing also fits. Without an account, a mailbox on this site is deleted a day after you last opened it, which suits a fast sale. Signing in stretches that to a week, recounted from every sign in, which covers the usual back and forth over price and collection. A negotiation running longer than that is a sign the deal needs a different channel anyway.

Which name to put on the listing

This decision is more consequential here than almost anywhere else, because a listing publishes the address to the entire internet rather than handing it to one form.

The address offered to you is generated to look like a mailbox a person would actually have: a word pair such as quietriver or a first and last name such as mia.reid, followed by four digits. That shape is deliberate on two counts. It does not announce itself as temporary, so it does not get flagged by a human reading a listing. And the four digit tail is a security decision rather than a cosmetic one: it puts the number of possible names on each domain in the tens of millions, where a two digit tail would have left a few hundred thousand, a space that one script covers over an afternoon, reading whatever it finds.

That matters because an inbox with no account behind it is unlocked by the address alone, with nothing else to present. On a listing you are publishing the key.

You can also type a name yourself. It has to be lower case, between three and thirty two characters, made of letters, digits, dots, hyphens and underscores, and it has to start and end with a letter or a digit. Around two dozen names are held back and cannot be taken, the ones that get written to about the domain rather than about you: admin, support, billing, postmaster, abuse, hello and their neighbours.

The advice for a listing is to resist the chosen name. sofa2024 is memorable to you and to everyone else, and memorable names on a public address are the ones that get guessed, which is also why they come back around into somebody else's hands sooner. Take the generated one, paste it, and never type it again.

Where it will hurt you

Warranty and returns. If you are the buyer and the item fails, the correspondence proving what was promised sits in a mailbox that no longer exists.

Disputes. Marketplace arbitration asks both sides for evidence. The messages are the evidence.

The buyer coming back. People who bought one thing and want another are the easiest sale you will ever make, and they cannot reach you.

Anything shipped. Tracking, delivery notices and courier problems all arrive by mail, and courier problems are exactly when you need the notice.

Two different addresses, not one

This is the part most people get wrong.

The account address is your identity on the platform. It holds your rating, your history, your payouts and your ability to recover the login. It must be permanent. Using a throwaway address here means losing the account and every review you earned the first time you forget the password.

The listing address is contact for one item. It can and should be temporary, because its whole job ends when the item does. It is the second of the four things people mean by a burner: an address that has to survive a conversation rather than a single code.

Many classified sites let you keep the account address private and communicate through a relay or a per-listing address, which does the same job. Where they do not, using a disposable address for the listing and a permanent one for the account gives you the same separation by hand.

Close it, do not wait it out

When the item is gone, delete the address rather than letting it expire on its own schedule.

The difference matters more than it sounds. An address that is still alive for another twenty hours is still collecting the scraped-list traffic and still usable by anyone who saved it. Asking for a new address here deletes the previous one immediately, so the gap between "sold" and "unreachable" is one click rather than a day.

Copy out anything you still need first. Deletion is immediate and nothing is recoverable.

If you are the buyer

The same address goes to a stranger, with one difference: you usually want the seller to be able to reach you until the item is in your hands.

So the buyer's timing is longer than the seller's. Wait until the item arrives and any return window has closed, then discard the address. If the item is expensive enough that a dispute is plausible, use an alias instead, which you can switch off later without losing the correspondence.

And be careful about which address you give a seller who is pressing for one. Sellers who move the conversation off the platform immediately, before any details are agreed, are following a script, and the first step of that script is getting you somewhere the platform cannot see.