Log syslog prefix MTA option

Syslog MTA options:  (bitmask)
New in MS 8.0.2.3. The  controls what prefix, if any, is attached to syslog messages generated by the   and   MTA options. The default is not to apply a prefix. Note that this behavior differs from previous releases, where the prefix was hard-coded to be "IMTA-W-".

See also:
 * Syslog MTA options
 * MTA transaction logging
 * log_connections_syslog MTA Option
 * log_messages_syslog MTA Option