Webflow website & mail accounts on private servers

Greetings everyone,
Firstly, i am very excited to be part of this huge community and i’m also very thankful that such tools like Webflow exist. As my first topic here on the forums, a very warm hello to everyone!

My situation is as it follows:
I have clients that would love to work with me developing their projects on Webflow, however there is a big issue with most big clients, that being the eMAIL addresses.

A workaround solution is to simply migrate their emails to let’s say Google business email, or Zoho premium emails and so on. However, some of my clients have security policies that prevents them to do so, and because of that, they need to keep the mail addresses on their internal company servers.

The issue with this is that some of the recipients, not all, will automatically decline their emails on the fact that their mail server cannot verify the source since they are checking it via the website’s location (which is dumb yes…)

As an example, this is an error message bouncing back
host [host name] [ip address]
SMTP Error from remote mail server after RCPT TO: [email address of remote user]
550 Client host rejected: no or inconsistent reverse DNS set.

I did found a couple of workarounds, like setting up a reverse DNS etc. but with some emails it still won’t work no matter what i do.

Can anyone guide me through to what can i do to simply use Webflow complete services but emails on a private server ?