Can I reply to an email in my temp inbox?

On most disposable-email services, including MailboxTemp, no. The inbox receives and displays mail but has no outbound path, so there is no reply, forward or compose button. A few services allow a limited reply to a message already in the inbox, usually without attachments and with tight caps. If you expect to reply, start with an alias or a secondary mailbox instead.

Why can't I send from MailboxTemp?

Because an anonymous, free address that could send would be abused for spam and phishing within hours, and the resulting blocklistings would stop verification emails reaching every other user. Sending also creates legal obligations that a receive-only service does not carry. Keeping the inbox one-way is what lets it stay free, anonymous and reliable for the job it is designed for.

Is there a temp mail that can send email?

A small number of services permit replies within the service, under limits such as no attachments, a message cap and a notice to the recipient. Paid or registered tiers sometimes offer fuller sending, but then the address is tied to a payment and an identity, which makes it a secondary mailbox rather than temp mail. For anonymous two-way email, an alias service is the closer fit.

What happens if someone replies to my temporary address?

If the inbox is still open, the reply appears there like any other message, and you can read it but not answer it. If the inbox has expired, the reply is refused or stored where you can no longer see it, and the sender is not told. Give a temporary address only to senders whose one message you need, not to people you expect to correspond with.

Can You Send Email From a Temp Mail Address?

Almost never. A temporary email address is built to receive, and nearly every disposable-email service, MailboxTemp included, will not let you send a message from it, reply to one or forward one on. The inbox is a window you can read through, not a mailbox you can post from. That is a deliberate design choice rather than a missing feature. If you need to hold a conversation, the right tool is an alias address or a secondary mailbox, and this article explains which to pick.

Why is receiving cheap and sending dangerous?

It helps to see the asymmetry. Receiving mail at a throwaway domain costs the operator almost nothing in risk. Messages arrive, sit in storage for an hour, and are deleted. Nobody is harmed by an inbox that only listens. The worst case for the service is that it fills up with junk nobody reads.

Sending is the opposite. The moment an address can originate mail, the service is vouching for whatever leaves it. Every message carries the service's domain in the From line, is signed by its servers, and counts against its reputation with every mailbox provider in the world. A free, anonymous, no-signup service that lets anyone send is an open invitation to exactly the people turned away everywhere else.

The four reasons services say no

The reasoning is the same across the industry, and it comes down to four points:

Abuse would be immediate. Spammers and phishers spend real effort finding places to send from, because sending capacity that is not tied to an identity is scarce. A disposable service with a send button would be the cheapest source of it on the internet. Rate limits do not help, because the abuse does not need volume per address; it needs volume of addresses, which a temporary-mail service supplies without limit.
Domain reputation is the whole business. A disposable-email service lives or dies on whether its domains can receive mail. Outbound spam would put those same domains on the blocklists mail servers consult before accepting a connection. At that point verification emails, the one thing users need, would stop arriving too.
Legal exposure. An operator that knowingly provides anonymous outbound email is in a very different position from one that merely receives it. Anti-spam law in many countries attaches obligations to whoever sends or facilitates bulk commercial mail. Fraud carried out through a service's own servers invites requests from authorities and complaints from victims' providers.
Nobody can be held to account. Ordinary providers can suspend an account or ask for identification when something goes wrong. A temporary-mail service deliberately knows nothing about its users; that is the privacy promise. The same promise makes sending impossible to police.

Receive-only is the design that keeps the privacy and drops the liability. The mechanisms receivers use to judge a sending domain are explained in SPF, DKIM and DMARC explained for normal people. How quickly a domain ends up on a signup block list is covered in why websites block disposable email addresses. The short version is that a domain's sending history follows it everywhere.

Are there temp mail services that let you send?

A few allow a limited reply to a message that is already in the inbox. The reply goes through the service's own servers under tight conditions: a cap on messages, no attachments, sometimes a delay, sometimes a visible notice to the recipient that it came from a disposable address. The logic is that replying to someone who already wrote to you is far harder to abuse than composing to an arbitrary address. The correspondent chose to contact that inbox first.

Even where this exists, treat it as a convenience rather than a channel. The address still expires, so any answer you get may land in a mailbox that no longer exists. The message is likely to be filtered aggressively on the receiving end. And the service may remove the feature whenever abuse rises. Some paid or registered tiers of otherwise disposable services also offer sending, but at that point you hold an account tied to a payment and an identity. That is a secondary mailbox under another name.

What to use when you need to reply

The right tool depends on how long the conversation needs to last and how much of your identity you are willing to tie to it.

An alias service

An email alias is an address on the alias provider's domain that forwards to your real mailbox and, crucially, lets you reply through the alias so the other party only ever sees it. You can create a different alias per correspondent and switch any of them off later. This is the closest thing to temp mail that can send: anonymous-looking to the recipient, two-way, durable for as long as you want, and cancellable. The costs are that the provider sees your mail in transit, and that free tiers usually cap the number of aliases. Email aliases vs disposable email compares the two models in detail.

A secondary mailbox

For anything that may need an attachment, a long thread or a reply months later, such as a marketplace sale, a job application or a landlord, a second free account at an ordinary provider is the honest answer. It can send, it keeps history, and it has a password you can recover, while still keeping your main address out of the conversation. It will ask for a phone number or a recovery address. That is precisely the accountability that makes it able to send.

Your real address, with a filter

If the other party is someone you would recognise on the street, such as a colleague, a tradesperson or a company you have a contract with, the simplest option is your real address and a folder rule. Privacy tools are for strangers.

Do you actually need to send?

A surprising number of "I need to reply" situations do not require a reply at all. Before reaching for a sending-capable address, check whether the site has a channel that does not depend on your mailbox:

A verification link only needs to be clicked; a code only needs to be typed.
Support requests usually have a web form or a chat widget.
Marketplace sellers can be messaged inside the platform.
A download or a discount code only needs the email to arrive.

Most sites offer one of these, because the email was only ever a way of confirming that someone was on the other end.

In short

Treat a temporary address as a one-way door. It is the right tool when all you need is for a message to arrive: a confirmation link, a one-time code, a gated download. The moment a conversation is involved, switch tools before you start rather than after the first reply fails.

Receive only, then forget: a temporary inbox.
Reply without revealing your address, keep for a while: an alias.
Attachments, long threads, recovery: a secondary mailbox.
Someone you already know: your real address.

If you are only receiving, there is nothing to work around, and how MailboxTemp works sets out exactly what the inbox does: receives, displays, expires.

Sources

RFC 7208, Sender Policy Framework (SPF), RFC Editor: how receivers check which servers may send for a domain.
RFC 6376, DomainKeys Identified Mail (DKIM) Signatures, RFC Editor: how a sending domain cryptographically vouches for its mail.
Email sender guidelines, Google Workspace Admin Help: the authentication and reputation requirements a large mailbox provider places on senders.
Domain Blocklist (DBL), Spamhaus: an example of the domain-reputation lists receiving servers consult.