To clear a macro, do not pass an argument in the map lookup. The map always returns the empty string. The arith map can be used to perform simple arithmetic operations. The two operands are given as arguments. All options which are possible for maps are ignored.
Some new macros are esp.
Multiple queue directories, and separate directories for qf, xf, and df files are possible. Better LDAP integration. Enhanced virtusertable support. Support multiple daemons, e.g., a message submission agent according to RFC 2476. Enhanced status codes as defined by RFC 2034.