Mail Delivery System <MAILER-DAEMON@smtp2.cybercity.dk>

Hvad stiller man op, når man ikke kan sende en mail og man får dette svar (jeg oplever det ved alle @sol.dk e-mails men også ved enkelte andre:

This is the mail system at host smtp2.cybercity.dk.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                  The mail system

<@.dk>: host mail.pote.dk[ipadresse] said: 554 Sending
    address not accepted due to spam filter (in reply to MAIL FROM command)