Tracking down a mail delay issue - mail server behind MT using dst-nat. Mail from the world frequently times out and doesn't make initial connection. I can duplicate this myself by getting outside of LAN and doing simple telnet - about 30% connection timeout. When on the LAN and using telnet, no timeouts. MT is used as edge router but CPU barely hits 5% (PC based).

Rule is simple dst-nat, there are no masquerades:
add action=dst-nat chain=dstnat comment="Mail Server" disabled=no dst-port=25 in-interface=ether1 protocol=tcp to-addresses=192.168.200.16 to-ports=25

Ideas?
Thanks
Ed

If there is no srcnat rule or masquerade, then that is why it fails.

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

If ether1 is not the connection to the internet (should be by the dstnat rule), change to the appropriate interface.

Sorry, didn't go far enough down in the config. There is srcnat translating the above local IP back to the correct (same as inbound) public IP.
Is there some debugging I can turn on or logging that might indicate why it frequently does not connect? Thanks

There is srcnat translating the above local IP back to the correct (same as inbound) public IP.

please post that rule