Import Postfix 2.10.2. Major changes since version 2.9.* are:
- Separation of relay policy (with smtpd_relay_restrictions) from spam policy
  (with smtpd_{client, helo, sender, recipient}_restrictions), which makes
  accidental open relay configuration less likely. The default is backwards
  compatible.
- HAproxy load-balancer support for postscreen(8) and smtpd(8). The nginx
  proxy was already supported by Postfix 2.9 smtpd(8), using XCLIENT commands.
- Support for the TLSv1 and TLSv2 protocols, as well as support to turn them
  off if needed for inter-operability.
- Laptop-friendly configuration. By default, Postfix now uses UNIX-domain
  sockets instead of FIFOs, and thus avoids MTIME file system updates on an
  idle mail system.
- Revised postconf(1) command. The "-x" option expands $name in a parameter
  value (both main.cf and master.cf); the "-o name=value" option overrides
  a main.cf parameter setting; and postconf(1) now warns about a $name that
  has no name=value setting.
- Sendmail-style "socketmap" lookup tables.