SMTP Proxy dual wan

Re questioning about this Bob.
Any chance for dual hostnames?

If there isn't an RDNS entry for an IP address, your mail will most likely be bounced. We actually had this with the setup I've just mentioned above as the A & PTR record hadn't been set up. Just enabling the 2 uplink interfaces pushed 50% of the mail out through the 2nd interface and it bounced.

Fortunately, we were watching for it and expecting it also. The solution was to create the multipath rule and chuck 100% smtp via the 1st interface until we got the A, PTR & MX records in place.

As far as I'm aware, most anti-spam solutions will do a reverse lookup first to make sure the sending IP has a valid A & PTR record with it. The mail will get bounced right there if the receiving server can't connect or find a PTR record. They will then move on to the more exotic stuff like SPF, DKIM & DMARC to increase or decrease the score.

We're quite pleased with our setup and are still tweaking it as we're in the process of completely switching the sites ie SITE B (failover site) will become the primary site in the event of an outage at SITE A (primary site) becoming offline for a reason.

Ok lets say the IPs have PTR and MX configured. What about SMTP Banner HELO?

For this i am worried

Never had an issue. As long as there is a PTR record for the sending IP, mail will usually flow. Think of a single server sending for multiple domains.

And of course, when you start to configure SPF etc, you would have to take into account the sending mail server/domain.

But the HELO/EHLO doesn't have to match the users domain. It just have to have an IP with a PTR which matches.

Thank you for the explanation. It will be your fault if  I go Blacklisted :)

here some test and strange behavior of my UTM 

"WorkUTM" has 2 UPLINK
Receives emails from both, but sends only from one (defined with mulipath rule). Second WAN not published in any DNS records etc.

HOW I tested sending emails to second IP? Simple, defined the mail.hostname.com with the second ip in my "homeUTM"
But my "HomeUTM" doesnt accept emails from my "WorkUTM" with the primary WAN-IP
[79.x.x.x]: 550 Invalid RDNS entry for 80.x.x.x

Tried to define the mail.hostname.com (work) with two IP, without success 

You know so much, Olsi, that I didn't think of this.  Like Louis said, you only need to make sure your authoritative name server entries tell the full story:

mail1.hostname.com A 22.33.44.55                     <-- EDIT 2018-02-22 Corrected mail2 to mail1
55.44.33.22.in-addr.arpa ptr mail1.hostname.com

mail2.hostname.com A 22.33.44.56
56.44.33.22.in-addr.arpa ptr mail2.hostname.com

v=spf1 ip4:22.33.44.55 ip4:22.33.44.56 -all

Cheers - Bob

Yes some DNS zones allow that

Found one article to edit exim.conf Bob 
And it works When i hit telnet 79.106.x.x 25, respond utm.xxxx.com
When I hit telnet 192.168.2.1 25 responds local.xxxx.com

Maybe its hard for developers to implement it

There can be very many domains hosted behind a single HELO string.  There must be tens of thousands behind mail-cys01nam02on0094.outbound.protection.outlook.com and the other servers for Office 365.

Cheers - Bob

I wanted only correct smtp banner for the correct IP, just that

I wanted only correct smtp banner for the correct IP, just that

I don't think that there's an RFC requirement that there be a different SMTP banner for different IPs or for different domains.  I can see that a hosting provider might not be set up like outlook.com and would want to offer customized SMTP banners for its customers.

Cheers - Bob