SMTP Reverse DNS Mismatch

Solution 1:

When your mail server identifies itself at SMTP time, it says its name is:

220 ns382087.ovh.net ESMTP

However, the SMTP server (obtained from grand-manitou.com's MX record) is actually mail.grand-manitou.com at 46.105.48.41.

The solution is to configure your mail server to identify itself correctly as mail.grand-manitou.com.

Solution 2:

I go another way. FOrget your domain, that has no part.

THe server name is ns382087.ovh.net - that is what the SMTP identifies itself as. Irrelevant what the domain is named that has the emails. OTherwise providers could not use one server for many domains (only one PTR ever exists).

The problem is that a PTR lookup on ns382087.ovh.net must include the IP of the server, and ns382087.ovh.net must go to the same IP. That way someone can see that yes, the server is the server that should be there.

Again, your domain is totally not part of that - this server check happens before the user email domain is checked. Just make sure your server name map forward and packward to the IP and that the SMTP agent uses the server name.

It is quite common for anyone outside smallest stuff that this is NOT the domain name - domains may be served by multiple servers. Or you may use a specific token name here (smtp.yourdomain...) All that is important is that the name of the SMTP service during handshake relates to the DNS in the proper way.

Check DNS and PTR for SMTP: shared IPs and subdomains for another explanation of things.