PPoossttffiixx aanndd LLiinnuuxx

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HHoosstt llooookkuupp iissssuueess

By default Linux /etc/hosts lookups do not support multiple IP addresses per
hostname. This causes warnings from the Postfix SMTP server that "hostname XXX
does not resolve to address YYY", and is especially a problem with hosts that
have both IPv4 and IPv6 addresses. To fix this, turn on support for multiple IP
addresses:

    /etc/host.conf:
        ...
        # We have machines with multiple IP addresses.
        multi on
        ...

Alternatively, specify the RESOLV_MULTI environment variable in main.cf:

    /etc/postfix/main.cf:
        import_environment = MAIL_CONFIG MAIL_DEBUG MAIL_LOGTAG TZ XAUTHORITY
    DISPLAY LANG=C RESOLV_MULTI=on

BBeerrkkeelleeyy DDBB iissssuueess

If you can't compile Postfix because the file "db.h" isn't found, then you MUST
install the Berkeley DB development package (name: db???-devel-???) that
matches your system library. You can find out what is installed with the rpm
command. For example:

    $ rrppmm --qqff //uussrr//lliibb//lliibbddbb..ssoo
    db4-4.3.29-2

This means that you need to install db4-devel-4.3.29-2 (on some systems,
specify "rrppmm --qqff //lliibb//lliibbddbb..ssoo" instead).

DO NOT download some Berkeley DB version from the network. Every Postfix
program will dump core when it is built with a different Berkeley DB version
than the version that is used by the system library routines. See the DB_README
file for further information.

PPrrooccmmaaiill iissssuueess

On RedHat Linux 7.1 and later pprrooccmmaaiill no longer has permission to write to the
mail spool directory. Workaround:

    # chmod 1777 /var/spool/mail

SSyyssllooggdd ppeerrffoorrmmaannccee

LINUX ssyyssllooggdd uses synchronous writes by default. Because of this, ssyyssllooggdd can
actually use more system resources than Postfix. To avoid such badness, disable
synchronous mail logfile writes by editing /etc/syslog.conf and by prepending a
- to the logfile name:

    /etc/syslog.conf:
        mail.*                          -/var/log/mail.log

Send a "kkiillll --HHUUPP" to the ssyyssllooggdd to make the change effective.

