virtual/mta
dev-perl/MIME-tools
sys-libs/pam
sys-libs/zlib

kerberos?
      ( virtual/krb5 )

sasl?
      ( >=dev-libs/cyrus-sasl-2 )

ssl?
      ( !libressl?
            ( dev-libs/openssl:0= )
       libressl?
            ( dev-libs/libressl:= )
       )

python?
      ( python_targets_python2_7?
            ( >=dev-lang/python-2.7.5-r2:2.7 )
       >=dev-lang/python-exec-2:=[python_targets_python2_7
            (-)
      ?
,-python_single_target_jython2_7
            (-)
      ,-python_single_target_pypy
            (-)
      ,-python_single_target_pypy3
            (-)
      ,-python_single_target_python3_4
            (-)
      ,-python_single_target_python3_5
            (-)
      ,-python_single_target_python3_6
            (-)
      ,-python_single_target_python3_7
            (-)
      ,python_single_target_python2_7
            (+)
      ] )

berkdb?
      ( sys-libs/db:* )