I dont receive e-mails with attachment sent to OS X Server 3.0.1 Group-mailing lists

I have a small company using a mac mini with mavericks and server 3.0.1.

We are using most of the services available in OS X server (except DHCP, Netinstall and Xsan). One of the services we use the most is Mail server, and the whole company uses that as our primary mail server.

We have set up several different Groups and activated group-mailing lists on some of them. The setup has been working very good for over a year (started using it with Mountain Lion Server).

Recently I was going to send a christmas card to all employees using the workgroup mailing list. I was using the stationaries in Mail, and it was sent as normal but never recieved by me or any of the other employees. Below is the SMTP Log

Dec 6 17:10:16 server.mydomain.com postfix/smtpd[29101]: connect from unknown[10.0.1.16 *<- my local IP address*]

Dec 6 17:10:16 server.mydomain.com postfix/smtpd[29101]: 480451503B0A: client=unknown[10.0.1.16 *<- my local IP address*], sasl_method=CRAM-MD5, sasl_username=myusername

Dec 6 17:10:16 server.mydomain.com postfix/cleanup[29109]: 480451503B0A: message-id=<CE56E99D-24C7-4F82-B91C-47C880177F92@mydomain.com>

Dec 6 17:10:16 server.mydomain.com postfix/qmgr[23288]: 480451503B0A: from=<myusername@mydomain.com>, size=98063, nrcpt=1 (queue active)

Dec 6 17:10:16 server.mydomain.com postfix/local[29110]: 480451503B0A: to=<workgroup@mydomain.com>, relay=local, delay=0.13, delays=0.05/0.01/0/0.08, dsn=2.0.0, status=sent (delivered to command: /Applications/Server.app/Contents/ServerRoot/usr/libexec/MailService/list_serve r_post post workgroup)

Dec 6 17:10:16 server.mydomain.com postfix/qmgr[23288]: 480451503B0A: removed

Dec 6 17:11:16 server.mydomain.com postfix/smtpd[29101]: disconnect from unknown[10.0.1.16 *<- my local IP address*]

I did some trial and error and it seems like it is linked to the fact that I have attachments to the email. Sending an email with only text is recieved like normal. Even attacment like PDF or jpg is "blocked" it seems. I have tried using email outside my domain but still the same result. Sending the same email (with attachment) to all reciepients (not using the mailiing list) works and is recieved by everyone. I have turned off all email filtering settings on the server but still the same result.

Is anyone else experiencing the same problem? My guess is that this is a Server 3.0.1 hickup, so it would be nice to get confirmation from others experiencing the same.