What the "Reverse DNS entries for MX records" message is about is not the MX records themselves, but the IP Address(es) that the MX reference points to. This is partially a manfestation of using Office 365, and somewhat out of your control. It may also be a function of the descriptive text used in the report.
Here's an example of an environment configured correctly. In the previous block "Differing mailserver addresses", I have this response from my MX record for my Office 365 domain.
184.108.40.206 has lawrencegarvin-com.mail.eo.outlook.com. | 220.127.116.11 listed.
18.104.22.168 has lawrencegarvin-com.mail.eo.outlook.com. | 22.214.171.124 listed.
The IP Address 126.96.36.199 is the actual mail server handling mail for my Office365 domain (lawrencegarvin-com.mail.eo.outlook.com).
DNSStuff expects to see a PTR record for that IP Address (the 'A' record for the hostname referenced in the 'MX' record) -- 188.8.131.52.
In your case this address appears to be 184.108.40.206, and it appears that this IP Address does not have a valid PTR record assigned. 207.46.163 does belong to Microsoft, and 163.46.207.in-addr.arpa is alive ... it would seem that the entry for '215' is missing.
Then, to confuse things a bit, a query on the MX reference (jskayconsulting-com.mail.eo.outlook.com) actually returned TWO different IP Addresses a few moments ago, and only one of those returned a valid PTR record. This is likely something you'll want to take up with Microsoft. It seems that either they have some records missing from the reverse lookup zone for this IP range, or there is something not-working-right in their DNS services for this reverse zone.
I got this response back from a query:
> set type=MX
jskayconsulting.com MX preference = 0, mail exchanger = jskayconsulting-com.mail.eo.outlook.com
> set type=A
> set type=PTR
*** <My DNS Server> can't find 247.163.46.207.in-addr.arpa.: Non-existent domain
220.127.116.11.in-addr.arpa name = mail-bn1lp0138.outbound.protection.outlook.com