maping address

[ot]

i don't understand the use of maping address
if i specify in my domains the type of rollernet service
for exemple smtp redirection or forward to an email address
why i have the posibility to specify another email address enabling maping address ?
is a redundance ?
thanks

[RollerNetSupport]

Address mapping will override any SMTP-level setting. If forwarding to an external address is enabled, it doesn't matter what mode the domain is in, as these settings will be ignored.