When I try to send a MMS message to someone I receive the error
message "2504:not enough funds". The message still remains in the
outbox of my Nokia N80 and won't be sent. All MMS configuration
entries are correct. Nokia says the error message doesn't come from
the phone, it is a network error message. EPlus (my German network
provider) says everything is all right and fully functional. The error
message MUST come from the phone.

Did anyone have similar problems with this?

When I plug in my Vodafone card and modify the MMS settings to
Vodafone, everything is working.

I guess it could be a malfunctioning SIM card of eplus. But this only
the result of logic. I cannot make a proof of it.

Perhaps someone can help me out.

Thanks Chris.