Felipe Alcacibar's questions

I have 2 servers and I need to forwart to internal port.

To explain I use the server with 2 interfaces (internal/external) as server A and the internal server as server B.

In server A i use

iptables -A PREROUTING -t nat -i $extif -p tcp --dport $extif_port -j DNAT --to-destination $dst_ip:$dst_port"
iptables -A FORWARD -t filter -d $dst_ip -j ACCEPT"
iptables -A POSTROUTING -t nat -p tcp -s $dst_ip --sport $dst_port -j SNAT --to-source $extif_ip"

And in the server B I use a fwmark and routing to the server A using fwmark and iproute2:

ip rule  $command  fwmark 1 lookup 1
ip route $command  default via $rt_ip table 1

--

iptables -A PREROUTING -t mangle -p tcp -i $intif ! -s $intif_net --dport $port -j MARK --set-mark 1
iptables -A PREROUTING -t mangle -p tcp -i $intif -s $intif_ip --sport $port -j MARK --set-mark 1
iptables -A POSTROUTING -t mangle -p tcp -o $intif -s $intif_ip --sport $port -j MARK --set-mark 1

Playing with the three rules above in the server B the connections only stuck with SYN_RECV state, and in the log does not sent the ACK in the connection, in some part the packet is loss internally, but i don't know why.

Any help is welcome, have a nice day.

I have a website, and the users recommend via email to another persons, so the mail come from my site, but I need to appear the user as sender, but "via" mydomain. The logically and what lists management software and companies do is differ the "MAIL FROM" SMTP command and the "From" header (like mailchimp, for example).

So I want to DKIM sign a mail with mydomain.com, even if the From header says another domain. is possibly this?

I am using postfix with Debian GNU/Linux, and in this case using dkim-filter and dk-filter.