where to setup virtual_mailbox_maps

Hello,

I have a domain in virtual_mailbox_domains:

aaa.com

I have also the virtual_alias_domains which include:

bbb.com

I know how to forward x@bbb.com to y@aaa.com by setting up the file "virtual_alias_maps":

x@bbb.com y@aaa.com

(and run postmap after the changes.)

But, how can I setup virtual_mailbox_maps (if I name this correctly)? for example, 111@aaa.com forwards to 222@aaa.com.

Thank you.