Tried to create my first server but it failed due to Outgoing address mapping file for Postfix (sender_connical_maps). The page says to configure it in the modules area but I can’t find where to do so and probably have no idea what to set it to.
Im not sure about sender_canonical_maps
but what I had to do to get things working was go under webmin-servers-postfix mail server
click "edit config files" (right pane) and all the way below add: virtual_alias_maps = hash:/etc/postfix/virtual
Ronald is close, but canonical maps is a different option.
sender_canonical_maps = hash:/etc/postfix/canonical
Or, you can simply disable the outgoing address mapping feature in Virtualmin (it helps to insure that mail sent from your system has the right "From" address…so if you have scripts that send mail, for example, it might be useful).