How do you generate .qmail file, or "you create it by yourself?"
If .qmail file doesn't not exist, then qmail-send will use it default to deliver the email.
what is default protocol?
If I want to use procmail and not dot-forward, what do I do?
It depends on how you are managing your qmail system.
Technically the .qmail-default file would be processed next if the .qmail for a user does not exist.
You can create the files manually on small systems, on larger systems some application for managing virtual domains are VMailMgr, vpopmail, and Qmail-LDAP.
Answer: Users can run
| preline procmail
from ~/.qmail. They will need to use a full path for procmail unless procmail is in the system's startup PATH. If you are moving from sendmail, and users have procmail in their .forward files: procmail will continue to work from .forward files if you have installed dot-forward. If you are moving from sendmail, and sendmail was using procmail instead of binmail: Copy /var/qmail/boot/proc or /var/qmail/boot/proc+df to /var/qmail/rc.