||Once, at the start of each SMTP connection.
||Do nothing; return SMFIS_CONTINUE.
||the opaque context structure.
||the host name of the message sender, as determined by a reverse
lookup on the host address. If the reverse lookup fails or if none
of the IP addresses of the resolved host name matches the original
IP address, hostname will contain the message sender's IP address
enclosed in square brackets (e.g. `[a.b.c.d]'). If the SMTP
connection is made via stdin the value is
||the host address, as determined by a
getpeername(2) call on the SMTP socket. NULL if the
type is not supported in the current version or if the SMTP
connection is made via stdin.
If an earlier filter rejects the connection in its
xxfi_connect() routine, this filter's xxfi_connect() will not be