email wont send

[HanJ]

Hi all

I have 3 email addresses running on the same server,
Info@mydomain
contact@mydomain
jeugd@mydomain

No issues when using the first two adresses, but when I send emails using the jeugd@ address, the emails never arrive, except on @hotmail.com receivers.

So sending an email with jeugd@mydomain to
[email protected] --> email arrives
[email protected] (or any other domain) doesnt arrive

Sending with info@mydomain or contact@mydomain, it arrives anywhere.
To make it even more complicated: this problem doesnt occur when I use squirrel mail instead of roundcube (but I prefer roundcube)

Hopefully anybody has a clue what is going on here.

Thanks!