550 5.7.511 Access denied, banned sender

whenever I send to outlook.com, I get the following error:

5.7.511 Access denied, banned sender[

the support page to delist my iP , sends back

Not qualified for mitigation
Our investigation has determined that the above IP(s) do not qualify for mitigation.

any body else have this problem

Goliath, being Goliath.

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.

where do you host your mail in a box

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 ( They currently report addresses of [Not Set]/[Not Set]. If you have set up External DNS, this may be OK.

How do you setup glue records on DO

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?

external Namecheap for now

Your domain currently does not have an a record.

The domain currently has no records … which is why I am confused…


The domain has MX, SPF, DKIM, and DMARC records as per MiaB standard for the domain. The subdomain has an a record, SPF record, Google verification.

OP has DNS pointed to NameCheap DNS, so a dig of the box does not count. The OP has added a MX record since I checked.

rDNS of the IP address reveals the domain, which is a DO IP address.

Comcast blocks me now, but I cannot find my ip on any spam sites.

Are there any messages in /var/log/mail.log for that transaction?

what transaction? for the returned email from outlook users?

Whichever transaction Comcast is blocking you. Just send an email and then check the logs. There isn’t always something there, but sometimes.

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.


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.

thanks, I had a sender score of 0

thanks, I had a sender score of 0, but while I am waiting to look at the product line, I just created a smtp relay on the free tier at sendgrid?