In Mailbox, function _verifyDepositLimit, the code after the if statement is never executed as address(0) is hard-coded and ETH deposits are uncapped (see the comment):
Although, AllowList, function setDepositLimit does NOT enforce it.
Consider changing it to revert if trying to cap ETH deposits.
Also, consider removing the whole _verifyDepositLimit function, as it will always return without modifying the state of the contract (tautology).
NOTE: Mailbox is for ETH, which is uncapped, and tokens are bridged via the bridges, which do check for the deposit limits themselves, so there is no place for that function here.
