Objective

I had some problems configuring my mail servers.

Obviously, to make it simple, I mix a lot of things, a Microsoft Tenant, domain names at OVH and hosting at Ionos, at one point, there is a configuration parameter that blocks.

I discovered a great site that in a few seconds checks everything for me and tells me if the DNS settings are compliant, if the SPF, KDIM, DMARC… configurations are up to speed.

Site used

This site is cute, simple and particularly powerful.

Operating principle

The site gives me an email address and I send an email to that address, simply then I press ‘Check your score’.

Result

At this stage, I have corrected everything, the reporting concerns of SPF or the activation of DMARC.

I have, in the end, 10/10

But I still have one point to improve:

This is the correspondence between the DNS pointer record (Type PTR) and the HELO, although the site detects that HELO and rDNS are not identical:

This seems to be a problem, for example with AOL messaging (still dinosaurs with AOL??) 

Of course, I did some research to see if it was going to be a problem or not.

Here is Microsoft’s response to this discrepancy between HELO and rDNS:

• https://learn.microsoft.com/en-us/exchange/troubleshoot/antispam-and-protection/cannot-send-emails-to-external-recipients

Microsoft explains in a few lines that they use several servers to send emails and that this seems to be the mode of operation of large platforms, they do not bring any solution apart from contacting the email provider who would refuse emails on which HELO is different from rDNS.

In short, obviously nothing shocking for them, I will remain so configured.