Digital Ocean is notorious for being the place that spammers go to spin up a mail server, spam, and then move on to the next IP. Because of that some ISP’s - namely Google and Micro$oft block entire IP ranges belonging to Digital Ocean.
Your potential solutions – get a new IP in a different Digital Ocean range, and hope for the best, use a different VPS provider, one which has not been thrashed by spammers, or use a SMTP relay.
I have developed a low cost SMTP relay for use with my MiaB’s and have it available now for others. If interested, PM for details.
I haven’t had or read about issues with Vultr IP addresses. Also, I notice that the developer of the OpenBSD project OpenSMTPD uses Vultr for his mail servers.
I have used various hosts. But at the moment I am using IntoVPS (Romania), Forpsi (Germany and Czechia), Buy VM (Las Vegas).
I have also had excellent results with LunaNode.
Nameserver glue records (ns1.box.firstsightmedia.com and ns2.box.firstsightmedia.com) should be configured at your domain name registrar as having the IP address of this box (104.248.41.112). They currently report addresses of [Not Set]/[Not Set]. If you have set up External DNS, this may be OK.
You don’t. They are set at the registrar. In this case with NameCheap. I am also seeing that your domain is using NameCheap name servers, not the MiaB.
I’m confused …are you intending to use External DNS or the MiaB for DNS for this domain?
Outlook and Microsoft are just a bunch of imbecile bits replying. Everyone gets the ‘does not qualify for mitigation’ reply.
I just went through the same.
Reply back and you will actually get a human (albeit from India) replying and asking you to explain why you should be mitigated, what caused the problem, and what you did.
Tip:
Check your reputation on Senderscore, and also register your IP on their own reputation system.
I basically replied pointing out that all those systems gave my server the green light, but their not did not.
24 hours later my server was removed and all was well.