When you submit a flight plan (IFR or VFR), it has to be sent to the ATC unit which is responsible for each FIR (Flight Information Region) which you intend to enter, the destination airfield, sometimes the alternate and sometimes airports which have overall responsibility for movements at adjacent, but smaller airfields.
For example, if you were flying from the UK to Southern Germany, you would be flying (depending on the route) through the at least one Dutch or Belgian FIR, and several German FIR's, all of which need to recieve your flight plan details.
The same applies to any other routing to any other destination, it can be as simple as crossing one FIR boundary or many, depending where you are going.
If the flight plan is IFR, it's sent to one "collective" address, which is a computer based in Brussels, if the route you've chosen corrolates to the information the computer likes, it automatically re distributes the flight plan to everyone who needs to know, if it doesn't, it tells you what it doesn't like and will not forward it until you get the route right.
In the case of VFR flight plans, these have to be addressed to every FIR ATC unit which you intend to cross.
In the case of both IFR and VFR plans, you are supposed to put the estimated elapsed time from departure airfield to the FIR boundary, this is not only so they know when to expect you but also so that if you don't arrive within 30 minutes of that time, they can start looking for you.
Either way, whoever you file your flight plan with is responsible for ensuring that the plan is sent to all the correct addressees.
Sorry if that's a bit long winded, but I hope it helps.