SMTP Routing via 'Additional Address'

Question

We have a range of external IP addresses, one of which is allocated to our MX record, I need to be able to send email out using that IP not the main WAN IP. At the moment some recipients are doing strict SPAM checking and rejectin our email as the originating IP does not match the MX Record. 
 All the related articles I have seen are many years old and refer to the Astaro device, the menus and solutions suggested do not apply or do not work. 
 So in summary our email goes out now on WAN I need it to go out on WAN-Additional_Address_MX_IP 
 Chees 
 SImon

Ol Deda · Answer

Have a look to "Multipath Rules". You already have a sample there

DouglasFoster · Answer

A SNAT might work, but I am not optimistic. 
 The easiest solution is to change the MX record, or add another one, so that the used IP address is authorized.

SimonBryan · Answer

Thanks Douglas - simple idea, went back to my DNS records checking the spf record ready to add the other IP - ooops had it as part of a range - but had typed it wrong! So had planned for this, forgot I had done that and had done it wrong. 
 Should work well now - which is good as I see no way to get Multipath rules working without multiple interfaces not just the additional addresses. 
 Cheers 
 Simon