Message format

Every message is a packed byte string. The Mailbox builds it in dispatch; recipients only see the parsed fields in handle.

Offset	Bytes	Field	Notes
0	1	version	3
1	4	nonce	Per-origin-Mailbox counter, starting at 0
5	4	origin	Origin domain id
9	32	sender	Sending contract, left-padded to 32 bytes
41	4	destination	Destination domain id
45	32	recipient	Recipient, left-padded to 32 bytes
77	any	body	Your bytes

The message id is keccak256(message).

The format is identical to Hyperlane's version 3, and messages can be decoded with the CLI:

rlink message decode --bytes 0x03…