ip rule add fwmark 2 table 3
ip route add default via 192.168.2.2 table 3
ip route flush cache
iptables -t mangle -A OUTPUT -p tcp -m multiport --dport 25,465 -j MARK --set-mark 2
iptables -t nat -A POSTROUTING -o ovpns1 -j SNAT --to-source 192.168.2.1
sysctl -w net.ipv4.conf.ovpns1.rp_filter=2

<rule priority="0" table="mangle" ipv="ipv4" chain="OUTPUT">-p tcp -m multiport --dport 25,465 -j MARK --set-mark 2</rule>
  <rule priority="0" table="nat" ipv="ipv4" chain="POSTROUTING">-o ovpns1 -j SNAT --to-source 192.168.2.1</rule>