[ale] Sendmail accept only local delivery on system accounts.

[lists at cruton.info (Giulio (lists))]

Hello alers,

My hosting provider has killed spamassasin ;-) and gave us Postini 
instead. I am not too crazy about it but it must be saving them a ton 
in bandwith.
Anyway I am trying to get spam under control but keep getting spam to 
local accounts e.g. info at domain. info is an alias.

Is there any way to tell sendmail to reject e-mails coming outside the 
localhost to the local accounts (root, info, postmaster etc.)?

It might be a dumb question but understanding sendmail is on my todo 
list. Probably will stay in the todo list for 3 more years.

Thank you.

Giulio