Reject the DATA or the session if a specified condition is true.
"nohelo" -- the client does not say "HELO"
"nofrom" -- the client does not say "MAIL FROM"
"pipeline" -- the client send command without waiting server's response
"nomx" -- the client's host does not have a MX record
"notselfmx" -- the client's host is not the MX of itself
"notmxhelo" -- the domain in the HELO is not the MX of the client's host
Multiple conditions can be specified concatenated with "+" as
SMTPCONF="reject:nomx+nohelo+nofrom+pipeline".
bgdatasize:N
If the data is larger than N bytes, relay it in background.
This means relaying a "DATA" command to a server without having a client
wait for the response for "QUIT" command from the server.
Note that only one mail DATA can be relayed in background and the mail
can be lost if the DeleGate crashes before finishing the forwarding
because the current DeleGate have no mechanism for spooling and
retransmission.
maxrcpt:N
Limit the acceptable maximum number of recipients (by RCPT commands)
Specify the SMTP server toward which mails
(bound for the domain) are forwarded.
The server can be specified based on the destination address of the
E-mail to be relayed (it is the address indicated in the RCPT command
on the SMTP protocol).
The character "*" in server is replaced with the
domain part of a E-mail address as "foo@domain".
The prefix "-MX." to a domain name as "-MX.domain"
represents the mail-exchange server of the domain
(which is retrieved by DNS as the MX record of the domain or host).
The default specification is
SMTPCONF="MX:{-MX.*,*}"
which means trying the MX first, and if it failed, then try direct
connection to the domain as a hostname.
Examples: SMTPCONF="MX:smtpserver"
-- use the smtpserver as the upstream SMTP server SMTPCONF="MX:{smtpserver1,smtpserver2}"
-- try the SMTP servers in the order SMTPCONF="MX:{-MX.*,*}"
-- the default configuration SMTPCONF="MX:{-MX.*,*,smtpserver}"
-- adding a backup SMTP server SMTPCONF="MX:{*,-MX.*}:*.localdomain"
-- forward directly to the host if it's in localdomain SMTPCONF="MX:smtpserver:{*.dom1,*dom2}"
-- a server for the specified domains
callback[:[T][:srcHostList]]
Callback to the SMTP server on the client host which is making
current request (on HELO command).
If there is not a SMTP server on the client host, then the
processing of the request will be delayed up to T seconds.
This could be effective to reduce DDoS type SPAM messages which
are relayed exploiting non-SMTP servers.
SMTPCONF="callback" is the abbreviation of SMTPCONF="callback:20:*".
