TLDR: Outlook.com appear to be junking all our emails from new VPS - nothing has an effect so questioning if IP address range reputation is the issue.
We used to host all our websites (five) and email on a single VPS. Due to email problems that we were unable to resolve we obtained another server from a different company (Hostinger) to host our email.
Everything has been set up ok as far as we know - SPF, DKIM, DMARC, reverse DNS, correct HELO etc. are all in place and we have tested our email set-up using MX Toolbox, Mail-tester.com and IntoDNS. Our emails have literally been scored 10/10 according to Mail tester.
Further test emails to Gmail and Hotmail confirmed that SPF, DKIM and DMARC have all passed the checks.
Despite this, large numbers of emails to our customers have been going into their junk folder - including long standing customers we have had no problem sending to in the past.
Nearly always, these incidents are to customers using Outlook.com as their mail provider - according to their MX records.
Even when we are replying to an email they originally sent to us it goes into junk. Our customers are marking our emails as 'not-junk' and then still the next one goes into junk.
Our IP address was on a blacklist before we started using it but we got it removed immediately.
We were then added to the UCEPROTECTL3 blacklist for a short while which, as I understand it, is as a result of activity from an IP address range rather than a single IP address.
We contacted our provider and got our IP address changed although the new one was very similar - ending in 207 as opposed to 215.
They have also avoided answering my questions about how we got onto that list and they insist that our IP address is perfectly fine.
I also read a couple of blog posts recently including:
Investigating this took a long time and it came out that there was a problem with various providers. They had "safe" ip's which they allowed and all the rest where just blocked and considered spam. This means that if you have an IP outside of a known and trusted range from a serious Web Hosting company then expect to have bad luck.
did have a link but had to remove
A previous ServerFault question had this as part of the answer:
If the only factor is your IP and you don't mail often, this might be "the reputation of the /24 my IP is in". If you mail a lot, you might get your own reputation.
The easiest way to get reputation which "drowns out" the IP reputation of your netblock is to set up DKIM. Send your mails signed. This will establish a per-domain reputation, instead of per-IP reputation, and provides more signal to the automated scoring systems.
did have a link but had to remove
However, I do have DKIM set up and test emails confirm that the checks have passed successfully.
So my question is, Do Microsoft (and/or other providers) automatically junk emails from certain IP address ranges?
If so is there anything, realistically, that I can do with our VPS to ensure emails get through?
some details removed due to, ironically, being accused of looking like spam...
