LinuxQuestions.org - DKIM for Postfix, Ubuntu 14.04

Hello,

I try to setip DKIM om my Ubuntu 14.04 server.
Its sending and recieving works, but heard that with DKIM it doesnt go to spam (Unless your spamming i guess)

I used mail-tester, and this where the results.
http://www.mail-tester.com/web-rTmQdH

Result of dig mail._domainkey.ditisgeenvirus.nl TXT
;; ANSWER SECTION:
mail._domainkey.ditisgeenvirus.nl. 599 IN TXT "v=DKIM1\; k=rsa\; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDRKbA8fokFvjF3uSnd5dEpa/h3JtGVofdjgopfHEAJBjc4aPC9tMCkdDU29NFbh9qjR3SjzBWzmehGoyBWh8Mz/uQrfoedOrMY1meutvNxoSesAiTt4/slf141hRflFyywXkfBavLvYr3i2WOJ+egvMgiCKArujc16o1Y+jzfQBQIDAQAB"

/etc/opendkim.conf got this (Not the whole file)
Domain ditisgeenvirus.nl
KeyFile /etc/postfix/dkim.key
Selector mail

The file and path it correct, and starts with:
-----BEGIN RSA PRIVATE KEY-----
Then the code.
-----END RSA PRIVATE KEY-----

Checked it with online tools and the DNS settings for DKIM should be fine.

Still it doesnt sign them.

EDIT: Got this when sending to my other email, wich i got for my domain package at mijndomein.nl

Quote:

host mail.***.com[188.***.148.***] said: 550
This host does not accept mail from unauthenticated sources. (in reply to
RCPT TO command)

Someone got an idea/tip where to look or how to fix this?

PS: Im using roundcube to send the mails, does this matter?

Hope someone can help me.
Jordy