Background:
I have an own domain and an own mail server that sends out the mail for this domain. The users are only my family so there are less than 10 users with probably 20 mails sent per day.
Please don't question why I have my own server: It is my job as a consultant to work with the server software and I use this server to test new settings / new versions before I use them in my customers' environments.
Until recently I used the relay server of my provider to relay all outgoing mails from my server. Now I changed my provider and relaying mails to their system is much more complicated as they do not have a whitelist but need authenticated connections.
Technical situation
- The server has a fixed IP address
- The IP address is entered in the SPF record
- There is a PTR record for that address that points back to mail.mydomain.de
- DMARC and DKIM are setup and strict rules are in place
- IP address is whitelisted at dnswl.org
Problem description
Sending mail from that server usually works fine. Unfortunately the German Telekom denies mails from the server as its reputation is not high enough. I contacted them and they answered "We don't take mails from personal mail servers. Send your mail to a relay, otherwise we will not accept it.
They pointed me to a link that lists the reputation services they query. One of them is SenderScore and there the reputation of my IP adress is 0 (=poor). Unfortunately they don't tell me anything useful about how to improve my IP reputation.
Question
Does anybody have an idea how I can improve my mail server reputation as a private person sending 20 mails a day max?