I've been running Postfix on my own dedicated server (hosted by Hetzner) for years, however, it's getting increasingly difficult get outgoing mail to Outlook/Hotmail and sometimes Google delivered. Outlook/Hotmail is almost always considering my mails as SPAM (unless when present on the address book).
The fix IP my box is running on has no issues, it's not on any abuse lists. And I try to do what I can to prove trustworthiness (Reverse DNS, SPF, DKIM).
It appears as if the entire IP range of dedicated servers hosted by Hetzner is on a "fishy list" from which an individual IP cannot escape. However, that's just a feeling, I don't see how I could find out why exactly Hotmail/Outlook classifying the way it does.
Is there a way to send outgoing mail by use of a provider who can guarantee better deliverability?
(I'm using Mailgun for transactional mails, basically, I'm looking for a way to configure Postfix to use such a service or SMTP.)
Thanks or your hints!