What is the correct entry format for an alias?
Right now I have
root: xxxx@somewebsite.com
Running newaliases -f /etc/mail/aliases
yields a syntax error. Are there examples in the manual page for aliases?
Your alias file format is correct but you are using the wrong file with the -f option, that's why its giving an error. See the relevant man page here:
https://man.openbsd.org/newaliases
-f file
Use file as the configuration file, instead of the default /etc/mail/smtpd.conf.
As you can see there, -f option is to use a configuartion file other than the default one and not the alias file itself.
You can just run newaliases
without any parameter and it should work.