Strange NAT behaviour - or just noob issue?

Hi this is my first stab at running a Mikrotik unit - an IBM x86 server running 6.0r13 at our office, in evaluation (free mode) before rolling it out in a small ISP and using BGP and queues to manage ISP customers.

My issue is when I connect to my mail server from a remote site, the mail server responds to the HELO with the Mikrotik router local LAN IP, rather than the WAN IP I am connecting from - have I screwed up my NAT rules?

NAT part from /export:

add action=masquerade chain=srcnat
add action=dst-nat chain=dstnat comment=“SMTP to Server” dst-address=x.x.x.x dst-port=25 protocol=tcp to-addresses=192.168.1.1 to-ports=25



Connection test from remote site y.y.y.y (remote LAN subnet = 192.168.2.1/24)

telnet x.x.x.x 25
220 remote.mydomain.co.uk Microsoft ESMTP MAIL Service ready at Wed, 1 May 2013
09:26:21 +0100
helo blah.com
250 remote. Hello [192.168.1.254]

Where x.x.x.x is the static WAN IP of the Mikrotik router and 192.168.1.254 is the LAN side of the Mikrotik and 192.168.1.1 is my mail server.

This doesn’t seem to be a huge issue, as currently the Mikrotik unit is handling Voip, queues, terminal servers and various other services on site admirably - just this discrepancy in the telnet output seems to be confusing our remote backup server which is bombing out on its backup reports that are supposed to relay through our exchange box.

Anyone got any advice? Perhaps i’ve just not been specific enough in my rules?

Thanks,

Guy

Add an out-interface to this nat rule:

/ip firewall nat
add action=masquerade chain=srcnat out-interface=ether1

If ether1 is not your WAN interface, change that to the correct interface name.

Add: If your email server stops responding when you add that out-interface, check the network settings in your email server. Insure you have the correct netmask and gateway.

Awesome. That fixed it.

Many thanks SurferTim!