The Mailbox Gateway functionality within a master device can be used to route the EtherCAT mailbox protocol from an (external) device configuration tool via the Mailbox Gateway to the EtherCAT devices and vice versa. All Mailbox protocols that are defined in the EtherCAT specification can be used in general, i.e. CoE, FoE, VoE, SoE.
There is no error handling specified for the Mailbox Gateway functionality. A request to a non-existing slave device can lead to no response from the master. According to Function Guideline „ ETG.8200 EtherCAT Mailbox Gateway“.

Mailbox Gateway Structure