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Mailchain users can send messages to any Ethereum account address. This section details how the Ethereum implementation of the Message Flow is achieved.


Mailchain supports all the common Ethereum networks

Network Status
Mainnet Full
Ropsten Full
Goerli Full
Kovan Full
Rinkerby Full

Public Key Finder

To send an encrypted message, a public key is required. Mailchain uses the public key associated with an account address to encrypt the data, and if specified by the envelope, the message contents. This ensures the recipient is also the owner of the private key and only they can decrypt data. The public key finder searches for transactions sent by the recipient address and extracts the public key.

{% hint style="info" %} The public key for an account address can either be calculated from a transaction signed by that account address or supplied by that account holder. In order to calculate the public key, the recipient address needs to have sent at least one Ethereum transaction. {% endhint %}


Ethereum transactions are used to send a message.


Transactions contain a data field that stores the envelope. Bytes can be stored in the data field and must be hexadecimal encoded, prefixed with 0x as per the Ethereum specification. Data stored in a transaction must follow the Mailchain standard encoding format:[protocol-prefix]+[mailchain-prefix]+[envelope].

Field Example Notes
protocol-prefix 0x Required Ethereum transaction data prefix
mailchain-identifier 6d61696c636861696e "mailchain" encoded as hexadecimal
envelope 010a82012ee10c59024c836d7ca12470b5ac74673002127ddedadbc6fc4375a8c086b650060ede199f603a158bc7884a903eadf97a2dd0fbe69ac81c216830f94e56b847d924b51a7d8227c80714219e6821a51bc7cba922f291a47bdffe29e7c3f67ad908ff377bfcc0b603007ead4bfd87ff0acc272528ca03d6381e6d0e1e2c5dfd24d521 Envelope encoded as hexadecimal

An example of transaction data for a Mailchain message sent on Ethereum is as follows:


The same transaction and data can be viewed on here on Etherscan.

Transaction Fields

To send a message these Ethereum transaction fields must be specified.

Field Type Example Notes
nonce unit64 8 Sequential number that represents the number of transactions the sender account has made on the network. Added by the client, based on last nonce.
gasprice unit64 0**.**00000002 Execution fee for sending the message. Added by the client, based on network gas price.
startgas *big.Int 30,660 Maximum gas used for sending the transaction. Mailchain messages uses ~30,000 GAS approx 1.5x the cost of a basic transaction. Added by the client, based on required gas.
to []byte 0x92d8f10248c6a3953cc3692a894655ad05d61efb Address of the recipient. Added by the client, based on recipient address in message.
value *big.Int 0 Set to send zero value transactions by default
data []byte 0x6d61696c636861696e.... Envelope data

Once the transaction fields have been populated, it must be signed using the sender private key. The signed transaction bytes can then be transmitted to the ethereum network over JSON-RPC using the eth_sendrawtransaction method.


To read Mailchain messages for a specific address, transactions sent to that address need to be identified. Ethereum does not natively support an address index or similar functionality that identifies all transactions sent to or from an specific address. Third parties have API's that provide this functionality, including

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