Most actions within XMTP do not incur typical gas fees as they occur outside of any blockchain. For instance, messages between addresses that have opted in to a connection can be sent without fees.
In some circumstances, a message may require a proof of postage to be submitted along with it. Proofs of postage are generated by interacting with smart contracts on L1 and L2 blockchains, and the actions taken there may require XTMP’s native token, and/or the blockchain’s token. More on postage here:
Some future use cases may involve additional on-chain contract interactions, which would require gas paid directly to the host blockchain.