Prior to V8, Sun's 
sendmail
 used the 
R
 option to cause all mail to be automatically routed to a mail hub machine. V8 
sendmail
 coopted the 
R
 option for its own use, so Sun had to switch the option name to 
>
. The 
>
 option is available only with V6/Sun, and above, configuration files.
The 
>
 option is used like this:
O>mailhub
If the entire 
>
 option is omitted, all mail is delivered locally.  If 
mailhub
 is present and if it is not the name of the local host, all mail is forwarded to that machine for delivery.  If the 
mailhub
 is omitted and if 
/var/mail
 is NFS mounted, all mail is forwarded to the host that is exporting 
/var/mail
.  The name of the 
mailhub
, no matter how it was determined, is assigned to the 
$K
 macro for use by rule sets.
Be aware that by setting and using this option, you are letting 
sendmail
's internals make all the decisions for you. If you prefer more control, investigate the 
nullclient
 FEATURE described in 
Section 19.6.20, FEATURE(nullclient)
.
The 
>
 option is safe.  When it is specified from the command line, 
sendmail
 retains its 
root
 privilege.