Outlook - Undelivered Mail Returned to Sender


I just tried to send an email to a hotmail address and got this?

 hotmail-com.olc.protection.outlook.com[XXX] said: 550 5.7.1
Unfortunately, messages from [XXX] weren't sent. Please contact
your Internet service provider since part of their network is on our block
list (AS3140). You can also refer your provider to
[SN1NAM02FT052.eop-nam02.prod.protection.outlook.com] (in reply to MAIL
FROM command)

I signed up to snds program by microsoft, and it does seem like that address is in their block list. But I did manage to send an email to hotmail a week ago.

There’s only been a few test emails sent by this host, and no other users. I guess it’s some other digital ocean spammers on this address range? Is this common?

All the various tests I could do for email passed, and sending to other hosts report no issues.

Looks like your VPS providers IP Address’s are blocked, I would talk to them first. It’s pretty common to happen to VPS providers, what I would do is contact Digital Ocean and get them to unblock the IP’s from Microsoft.

Or you could get a dedicated server like from nocix.net.(As an example) which will give you IP’s instead of sharing a whole block.

Ok, thanks a lot for your reply. I reported it to them. Fingers crossed!

I guess I should consider a dedicated server then.


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I have been with nocix.net (US based) for over 4 years now. They work great, simple and cheap. and full control over what I use them for. Never had an issue with IP Block blacklisting with them, but results will vary.

Good luck!

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Also, did u set SPF records in your DNS settings? Or possibly DNSSEC?

outlook and hotmail are known for spamming… not microsoft but the users who sign up for their services, this might be the problem. Or your IP address is blacklisted because someone who had that IP before you used it for malicious purposes… those are 2 possibilities.

The SPF, DNSSEC, etc pass all the tests I’ve been able to find.

Now, I joined up to the outlook junk program - snds. https://postmaster.live.com/snds/

Registered the ip address of the server, signed a contract (click click). After a few days I got a response that the ip address was removed. Three days later it started accepting email, and sending it to junk. Now it seems to be going through… to the people I asked. But maybe they just clicked not-spam, and now it makes it through to them.