It can be a problem to send mail from a different mail server than 'your own'. The reason for this is that the world is trying to fight the ridiculous amount of spam that floods us in general and one of the weapons in this quest is called "TXT record" which basically means that the owner of a domain (www.example.com) will register which servers are authorized to send out mail for that domain. As a start it is mainly hotmail, outlook and live.com (Microsoft) who has enforced this by rejecting mails from unauthorized servers but others are following.
This means that if example.com wants to send out mail via for instance a service for news mails, via a financial program and via KeepTrack you have to register all these servers with a DNS TXT under your own domain.
You can follow this link http://www.spfwizard.net/ to use the wizard for making your own spf-text. Add _spf.keeptrack.dk for keeptrack.dk
If you only send mail via MX the spf part of your DNS TXT should look like this: v=spf1 mx a include:_spf.keeptrack.dk ?all
Test spf settings http://www.kitterman.com/spf/validate.html
Check your domain settings https://dnscheck.gratisdns.dk
Check your spam status https://www.spamhaus.org/lookup
If you do not understand the above we strongly recommend that you seek assistance from an expert consultant.
Apart from the above settings Microsoft has its own service where you should register KeepTrack as an approved sender of your e-mail.
If you are anyway in doubt whether you have registered just go to the website again and enter the same data. Microsoft will then tell you whether or not you are already registered.