This means that chekoslovakia or ussr, or hungary wont be eligible to be changed?
Definitives are not always common. For instance, definitives from, lets say, surinam, or even slovenia, or bielorrussia. Or many series from uk, germany,....
The problem usually is sending the most common definitives from the most common countries.
Maybe a possibility, probably difficult to program, is to assign a slot, then the user reads the profile.
If the user thinks he's not able to fulfill the requirements, then, the user has the possibility of reject the slot, and "jump", to another user.
For instance, I'm assigned to a collector that dont want cto, definitives, and only wants fauna and flora.
I don't feel comfortable with this, so, I reject the slot, and jump to another.
The following user wants stamps from Australia, or, maybe, accepts anything.
I like this slot, so I send the stamps.
If we change the rules, and decide, for instance, that definitives, or cto cannot be sent, I think that the initial idea of this website will be seriously weaken.
There are lots of webs for direct swaps.
So, maybe we shouldn't change the rules, and simply ban the users that are sistematically rated low, as you propose in the other message.