Message Failure & Retry

Message execution may fail on the destination chain for the following reasons :

1. gasLimit required for message execution on the destination chain execeeds the msgGasLimit set for message delivery on source Plug
2. Fees sent on source chain do not cover the message execution fees on destination chain
3. The inbound call on the Plug is failing, which may happen if there's some logic in the inbound method that's failing.
4. The packet which includes the message is not verified yet

Executors simulate the message execution transaction and check for its success. If it's successful, they execute the message on-chain. Else, they keep trying to simulate the transaction for 2-3 hours, after which they stop. Currently, the message is untended and would have to be sent again from the source chain.

In the first and second case as well, Plugs cannot make a fallback action to execute the message. The message would have to be sent again from the source chain.