looks up MX records for the fully-qualified domain name in
It puts the MX records into
and returns 0.
Each MX record is a two-byte MX distance followed by a \0-terminated
dot-encoded domain name.
If the domain does not exist in DNS, or has no MX records,
will be empty.
has trouble with the DNS lookup or runs out of memory, it returns -1,
It may or may not change
is a low-level component of
designed to support asynchronous DNS lookups.
It reads a DNS packet of length
extracts the MX records from the answer section of the packet, puts the
and returns 0 or -1 the same way as