Searches DNS for MX records corresponding to hostname. Returns TRUE if any records are found; returns FALSE if no records were found or if an error occurred.
A list of the MX records found is placed into the array mxhosts. If the weight array is given, it will be filled with the weight information gathered.
注: This function should not be used for the purposes of address verification. Only the mailexchangers found in DNS are returned, however, according to RFC 2821 when no mail exchangers are listed, hostname itself should be used as the only mail exchanger with a priority of 0.
See also checkdnsrr(), gethostbyname(), gethostbynamel(), gethostbyaddr(), and the named(8) manual page.