Well, if all your IP addressees have a good reputation, no. There is no improvement in doing this.
However, this addresses a different issue, that may have a big impact.
By doing this, I’m making sure the primary IP address of the server is not mentioned in the header “Received: from” of e-mails my clients send, thus, I’m mitigating a risk of my primary mail server IP being blacklisted in case a client does something stupid, like forward their mail (including incoming spam), creates unprotected web form, or goes overboard by sending numerous e-mails without making sure their IP reputation can take it, to g-mail, y g-mail wannabe or worse of all outl00k who will in a second blacklist any IP suspected of being a spam relay.
After this change, any stupid thing my client does affects only his IP, so my behaving clients on shared plans will not suffer a poor deliverability a blacklisting of main server can cause.
I don’t even mind blacklists. If you do something stupid, suffer. But did you ever try to fix poor deliverability issues to outl00k and affiliated services? It’s a nightmare!
First they point you to oriffice365 IP delist, then, they ask you to send a ticket to each of their services deliverability support, then they ask you to join their Junk Email something program, then their something, something Services Program. Weeks of costly fun.
The worst thing is, they act as they are solution to the spam problem, when in fact, they, as a free(mium) provider are a largest part of the cause. Funniest thing is, most of the e-mails from their support ended up in my spam folder, and I use only out of the box SA config. Poor incompetent arrogant bastards are lucky they have all the money Bill made, because if they were a startup, they would have died in a first year.
In a nutshell, SPF, DKIM and DMARC are most important. Hell. I even implemented f…in’ BIMI, although I’m all against it, as it will only benefit large corporations and will have little to no effect in real spam prevention.
But that’s all just your basic server hygiene. Everything about deliverability is REPUTATION, and this single config line is just one of the numerous attempts I make to build and keep it.
Sorry the answer turned into a rant, but I drink on Sundays, and as I forbid myself the access to my servers and social accounts during Sunday evenings, I just couldn’t help myself, and shared thse ramblings with you guys.