How Temporary Email Works Behind the Scenes

When you open TempoEmails, an email address is already waiting for you. You didn't fill in a form or choose a password, yet a minute later a confirmation code sent to that address shows up on the page. This article explains how that works: what the mail providers do, what TempoEmails does on top of them, and where your messages are kept.

1. How a Provider Receives Mail for Any Address

Email is delivered with the Simple Mail Transfer Protocol (SMTP, RFC 5321). When a website sends a message to [email protected], its mail server first looks up the MX (Mail Exchanger) records for example-temp.com to find out which server accepts mail for that domain:

It then connects to that server on port 25 and hands over the message:

1. EHLO sender.com: the sending server introduces itself.
2. MAIL FROM: <[email protected]>: the return address.
3. RCPT TO: <[email protected]>: the recipient.
4. DATA: the headers, body and any attachments.
5. QUIT: the connection closes.

Accepting Mail for Addresses Nobody Registered

A company mail server (Google Workspace, Microsoft 365) checks whether user_8492 is a real mailbox and rejects the message with an SMTP 550 5.1.1 User unknown error if it isn't.

A disposable email provider works differently. Depending on the provider, it either accepts mail for any name on its domains (a "catch-all") or lets anyone create a mailbox through a public API in a single request. Either way, an address is usable the moment it's chosen, with no registration step.

2. Where TempoEmails Fits In

TempoEmails doesn't run its own mail servers. It's an interface on top of several public disposable email providers:

• Mail.tm and Mail.gw: TempoEmails creates a real account through their API, with a random password. The password is shown under "Access", so you can reopen the inbox later in another browser.
• Inboxes: a catch-all service. Any name on its domains works, and the inbox has no password.
• TempMail.lol: creates an inbox with an access token. The inbox expires after about an hour.
• Guerrilla Mail: a long-running service with session-based inboxes and no password. It deletes messages after about an hour.

When the page loads, TempoEmails asks all of them which domains they currently offer and picks one at random. If creating the inbox fails, it moves on to the next provider: Mail.tm, then Inboxes, TempMail.lol and Guerrilla Mail. If none of them respond, you get a clearly labelled simulated inbox that can't receive real mail, rather than an address that silently goes nowhere.

Most providers don't accept requests from other websites' pages, so your browser talks to them through a small relay on the TempoEmails server (/api/mail/). The relay only forwards requests to these providers, limits how many requests one visitor can make per minute, and doesn't store messages.

3. How New Mail Reaches Your Screen

Mail arrives at the provider, not at TempoEmails. To find it, the page asks the provider for the message list every 10 seconds while the tab is open; a small progress bar shows the countdown. When something new appears:

• The full message is fetched and cached in your browser (in localStorage), so you can still read it if the provider deletes it a few minutes later.
• Codes and links are picked out. TempoEmails looks for 4–8 digit codes near words like "code", "OTP" or "verification", and for https confirmation links, and shows them above the message with a copy button. Read more in our guide to OTP verification codes.
• The HTML is cleaned before display. Scripts, forms and other active content are removed, 1x1 tracking pixels are stripped, and the message is shown in a sandboxed frame. See what email tracking is and how to block it.

4. Why Some Sites Reject Disposable Addresses

Public lists of disposable email domains exist, and some sites check signups against them. When that happens, nothing you do in the inbox will help, because the site never sends the email. What does help is switching to an address on a different domain: click "New Email" for a random one, or "Custom" to choose the name and domain yourself.

5. Where Your Messages Are Stored

• At the provider, for as long as that provider keeps them. Retention varies: TempMail.lol inboxes expire after about an hour, Guerrilla Mail deletes messages after about an hour, and other providers may delete inboxes whenever they choose.
• In your browser, as a cache of up to 100 recent messages per address, until you delete the inbox or clear your browser data. Your last 25 addresses are kept too, so you can switch back to one.
• Not on the TempoEmails server. The relay passes messages through without saving them.

Deleting an inbox in TempoEmails removes it from your browser; it doesn't delete it at the provider. Deleting a single message also asks the provider to delete its copy, where the provider supports that.

Inboxes without a password (Inboxes, Guerrilla Mail, TempMail.lol) can be read by anyone who knows the address. Use them for throwaway signups, never for anything you'd mind a stranger reading.

What Temporary Email Is Good For

1. Keeping your main inbox clean: follow-up newsletters and promotions go to an address you can abandon. More tips in our guide on how to avoid spam emails.
2. Limiting exposure: fewer companies hold your real address, so fewer breaches and phishing campaigns can reach it.
3. Testing: developers can sign up to their own app with several addresses to check confirmation and password-reset emails.

Summary

Disposable email works because providers accept mail for addresses nobody registered. TempoEmails sits on top of several of those providers: it picks one, polls it every 10 seconds, highlights the code you're waiting for, and keeps a copy of your messages in your browser. The providers hold the mail; TempoEmails makes it easier to use.

For more on keeping your accounts safe, read our guide to online account security, and see the Privacy Policy for the details of how data is handled.