Installation of qmail

1. Create the qmail home directory: # mkdir /var/qmail
2. Set up the qmail group and the qmail users before compiling the programs.

First add two new lines to /etc/group :

qmail:*:2107:
nofiles:*:2108:

where 2107 and 2108 are different from the other gids in /etc/group.

Next (using vipw) add six new lines to /etc/passwd, something like

            alias:*:7790:2108::/var/qmail/alias:/bin/true
            qmaild:*:7791:2108::/var/qmail:/bin/true
            qmaill:*:7792:2108::/var/qmail:/bin/true
            qmailp:*:7793:2108::/var/qmail:/bin/true
            qmailq:*:7794:2107::/var/qmail:/bin/true
            qmailr:*:7795:2107::/var/qmail:/bin/true
            qmails:*:7796:2107::/var/qmail:/bin/true

where 7790 through 7796 are _new_ uids, 2107 is the qmail gid, and 2108 is the nofiles gid. Make sure you use the nofiles gid for qmaild, qmaill, qmailp, and alias, and the qmail gid for qmailq, qmailr, and qmails.

3. Compile the programs:                                                       # make
4. Create the formatted man pages, *.0:                     # make man
5. Create the qmail directory tree:                                    # make setup
6. Run instcheck to make sure it doesn't print any warnings:        # make check
7. Read INSTALL.ctl and FAQ.
                    Minimal survival command:                                   # ./qmail-config
8. Read INSTALL.alias.
                    Minimal survival command:
       # (cd ~alias; touch .qmail-postmaster .qmail-mailer-daemon .qmail-root)
       # chmod 644 ~alias/.qmail*
9. Read INSTALL.mbox.
10. Read qmail-upgrade.0. This is what your users will need to know
    about the switch from sendmail to qmail.

Upgrading from sendmail to qmail

Read INSTALL.boot. You must replace the sendmail invocation in your boot scripts with an appropriate qmail invocation.
Kill the sendmail daemon. You should first kill -STOP the daemon; if any children are running, you should kill -CONT, wait, kill -STOP again, and repeat. If there aren't any children, kill -TERM and then kill -CONT.
Replace sendmail with a link to qmail's ``sendmail'' wrapper:
# mv /usr/lib/sendmail /usr/lib/sendmail.bak
# ln -s /var/qmail/bin/sendmail /usr/lib/sendmail

Set up qmail-smtpd in /etc/inetd.conf (all on one line):
smtp stream tcp nowait qmaild /var/qmail/bin/tcp-env
tcp-env /var/qmail/bin/qmail-smtpd

Reboot. (Or kill -HUP your inetd and make sure the qmail daemons are running.)
Try to flush the sendmail queue:
# /usr/lib/sendmail.bak -q
You can safely run sendmail.bak -q (or even sendmail.bak -q15m) while qmail is running. Do this until the sendmail queue is empty.This may take several days.

Disable all the sendmail and binmail programs in your system. The safest approach is to chmod 0 everything. Some locations to check:
/usr/sbin/sendmail, /usr/lib/sendmail.bak,
/usr/lib/sendmail.mx, /bin/mail, /usr/libexec/mail.local.

Differences after the system switches from sendmail to qmail

qmail-local sends incoming mail to ~you/Mailbox by default, not /usr/spool/mail/you. Your system administrator has changed your MAIL environment variable so that your mail reader looks for ~you/Mailbox. (/usr/spool/mail is a massive security problem.)

qmail-local pays no attention to .forward. It has a much better mechanism, .qmail, so that you can handle not only forwarding but even your own mailing lists.

qmail-local pays no attention to /etc/aliases. Your system administrator can use the .qmail mechanism instead.
qmail-inject has a completely different philosophy from sendmail on interpreting non-fully-qualified host names. It uses fixed rules, not DNS. Some examples at UIC:

               russet   ------>       russet.math.uic.edu
               newton ------>       newton.math.uic.edu
               ut.ee     ------>       ut.ee (a host in Estonia)
               ut.ee+   ------>       ut.ee.uic.edu
               uicvm+ ------>       uicvm.uic.edu

default domain name

math.uic.edu

plus domain name

uic.edu

Unlike sendmail, qmail-inject doesn't replace host names with canonical names.
Example:
qmail-inject won't change   postmaster@ftp.cs.berkeley.edu in your header to                               postmaster@kohler.cs.berkeley.edu.

qmail-local adds a new field, Delivered-To, before every delivery. It uses the contents of Delivered-To to prevent mail forwarding loops.
If you send a message with only Bcc recipients, qmail-inject will add
Cc: recipient list not shown:;, rather than sendmail's privacy-invading Apparently-To header field.

QMAIL MAILING LISTS

sendmail deals with aliases, forwarding, and mailing lists at the very heart of the mail system. qmail takes a radically different approach. It gives you the power to set up your own mailing lists without pestering your system administrator.
Under qmail, you are in charge of all addresses of the form you-anything. The delivery of you-anything is controlled by ~you/.qmail-anything, a file in your home directory.

Example: if you want to set up a bug-of-the-month-club mailing list, you can put a list of addresses into ~you/.qmail-botmc. Any mail to you-botmc will be forwarded to all of those addresses. Mail directly to you is controlled by ~you/.qmail. You can even set up a catch-all, ~you/.qmail-default, to handle unknown
you- addresses.

Your .qmail files, like your old .forward, may list files, forwarding addresses, or other programs to run. (But beware that the syntax is a bit different; see dot-qmail(5) for more details.) qmail-local automatically detects forwarding loops the instant they occur, even if they happen indirectly through other hosts.

Addresses that don't contain a username are handled by the alias user. For example, your system administrator has set up ~alias/.qmail-postmaster to handle mail for Postmaster.