Even though Qmail is considered as obsolete email server lately and it lacks good systematical official documentation and requires a lot of "hacking" to make work. It is surely still the fastest and maybe securest mail server out there (if properly configured).
My Qmail uses Vpopmail (for Virtual Email hosting). Every now and them some client requires to add a new e-mail forwarding from E-mail email@example.com to Email to firstname.lastname@example.org. Though many like to use Web interface as QmailAdmin for adding the forward I still prefer do it via old fashioned way, by SSH-ing to qmail server host and manually creating .qmail file.
Location (of my Vpopmail) install is (/var/vpopmail), so (to add e-mail forwarding for sample mail – email@example.com) .qmail file needs to be created in dir /var/vpopmail/domains/host.com/mail/ with content:
qmail:~# echo '/var/vpopmail/domains/host.com/mail/Maildir/' > /var/vpopmail/domains/host.com/mail/.qmail
qmail:~# echo '&firstname.lastname@example.org' >> /var/vpopmail/domains/host.com/mail/.qmail
First file instructs, where to store a copy of received e-mail (copy is stored in Maildir of receipt e-mail).
In Second line is mail to which to forward. For forwarding to group of e-mails all e-mails has to be listed in .qmail, i.e.:
Finally to make just created .qmail file work peroperly user group permissions has to be fixed:
# chown -R vpopmail:vchkpw /var/vpopmail/domains/host.com/mail/Maildir/.qmail