I have a problem with sending mails using IPv6.
We have one WAN interface with the following settings:
WAN2 on eth2 [xx.xx.xx.162/29 | co:ff:ee::2/64]
MTU 1492 · DEFAULT GW xx.xx.xx.161 | co:ff:ee::1
We have some more IPs assigned to the interface in the additional addresses tab. Everything is set up in dual stack with both IPv4 and IPv6.
One of the additional addresses (for a webserver) got the ips xx.xx.xx.165 and co:ff:ee::cf36.
We use SMTP Proxy and mails going to IPv4 mailservers are send (just like they should) over the WAN2 using the xx.xx.xx.162.
But somehow mails going to IPv6 mailservers are send over the additional address co:ff:ee::cf36 and not over the IPv6 from WAN2 interface.
At least I want to understand why the UTM is using the co:ff:ee::cf36 for sending IPv6 mails ant not the co:ff:ee::2 from WAN2 but best I would like to change the UTM to use the co:ff:ee::2 for sending IPv6 mails.
I already read this thread https://www.astaro.org/gateway-products/mail-protection-smtp-pop3-antispam-antivirus/48039-smtp-ip-different-ip-then-utm.html but I am not sure if the SNAT workaround would help me.
Is there another option than the SNAT rule? If no, what should my SNAT rule looks like?
Best regards
Christian
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