If there is one thing that was really missing in CB compared to phpBB-like boards, that was the possibility to edit our own private messages in order to correct, add or update a detail, and this missing function had a lot of influence on our inboxes and outboxes' filling up.
It's now solved since this night, as I worked on developing a MOD that brings this function, and after having done local testing to ensure everythings works fine, I sent the modified files.
For those who speak French and run a CB forum, the MOD is available on the official website.
And by the way, even if I increased the outboxes and inboxes capacities for all groups, I remind everyone to clean up their inboxes and outboxes regularly, in order to prevent PM sending or reception problems caused by full box.
I also took the opportunity to correct the small bug in the downloadable forumotion styles management, and the bug was actually very simple : it was a question of case, as the forumotion version names in the styles' data were all lowercase while the values in the drop-down menu for version choice in the form had capitals ! So, I corrected this detail.