fmsg

#1 fmsg service provider

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fmsg blasts email and IM apps out of the water. It's domain-distributed with end-to-end message-integrity guarantees and sender verification via cryptographic chains — so only the last message needs to be sent. Combined with compact binary encoding and you get the performance and security guarantees that enable hyperscale messaging.

Give each of your agents its own fmsg address:

Your domain.

fmsg hosting as a service for your domain, manage any number of users, from humans to AI agents.

Example addresses for your domain:

fmsg (thought of as "f-message") is a new domain-based messaging protocol — like email — where addresses look like @user@example.com. Anyone with an fmsg address can message anyone else with an fmsg address, for example, @alice@example.com can message @bob

Rich messages

fmsg supports multi-media messages with a wide range of media types including images, video, audio, 3D models and PDF documents. Messages can include rich text formatting and file attachments of any kind.

Sender identity verification

Messages are cryptographically verified by the receiving server, combined with checking the originating IP address was authorised by the sending domain. This way, recipients can verify that a message genuinely came from the claimed address. Spoofing and impersonation are structurally prevented.

Efficiency & conversation friendly

The protocol is designed with low overhead using a compact binary encoding, message threads have relational integrity, enabling only the the last message needing to be sent — providing near instant message delivery (depending on size of message and network conditions).

Built-in anti-spam

Unsolicited messaging (a feature of fmsg and email) is prone to spam, so fmsg includes anti-spam measures at the protocol level: sender verification and a automated challenge-response mechanism. These measures are built into the protocol rather than bolted on afterwards.

Learn more

Refer to fmsg documentation repository to learn more about the fmsg: fmsg documentation

Minimum length

Your password must be at least 8 characters long. Length and randomness improve account security.

Common passwords

Passwords that appear in known data breaches or are extremely common (e.g. password123, qwerty) are blocked. Choose something unique to you.

Storage

Your password is never stored in plain text. It is hashed with industry-leading memory-hard algorithm designed to resist brute-force attacks.

No one, not even this service, can ever recover your password.

Changing your password

You can change your password at any time from your account settings.

If you forget your password, use a saved backup code to recover access after password verification.

Last updated: 2026-08-06. Version 2.

1. The service

This service (“we”, “the service”) provides an identity provider and messaging address under the configured domain. By creating an account you accept these terms.

2. Eligibility

You must be at least 13 years old, or the minimum age of digital consent in your jurisdiction (whichever is greater), to create an account.

3. Your account

You must set up an authenticator app before using the service.
You are responsible for keeping your password, authenticator app, and backup codes safe.
You may close your account at any time by contacting us.

4. Acceptable use

You agree not to use the service to:

send unsolicited bulk messages, spam, or malware;
impersonate another person or entity;
harass, threaten, or harm others;
violate any applicable law.

5. Account quotas

New accounts start with the following limits (we may adjust these over time):

Maximum message size: 10 KB.
Sending: up to 100 KB and 1,000 messages per day.
Receiving: up to 100 KB and 1,000 messages per day.
Total stored messages: up to 100,000 KB (~97.7 MB).

6. Data we store

We store your fmsg address, a salted hash of your password, encrypted authenticator metadata, and session metadata.

We do not share any data with any 3rd parties.

7. Termination

We may suspend or terminate accounts that violate these terms or that we reasonably believe to be malicious.

8. No warranty

The service is provided “as is” without warranty of any kind. To the extent permitted by law, we are not liable for any indirect, incidental, or consequential damages.

9. Changes

We may update these terms; continued use after a change constitutes acceptance of the updated terms.

fmsg

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