2
Yeah - that would be a good enhancement for the PM module that ships with the XOOPS core.
There is an alternative to the PM module.... try Lord Vernom's mpmanager which is now at v2.74 and has been coded for XOOPS 2.3.x - it is much more fully featured than the PM module and is more like a webmail service where your users can send files, etc to each other.
See this News item:
https://xoops.org/modules/news/article.php?storyid=4619&com_id=44698&com_rootid=44098comment44698
The there is a link to v2.74 in a comment-post by LV himself
You'll need to deactivate/uninstall the PM module before installing mpmanager