I haven't had any permissions problems per se, but Squirrelmail in an ibay just isn't particularly secure. The members of the group that has read/write permissions to the squirrelmail ibay, (which may be the "Everyone" group), have full access to the folder structure through samba. Also, if you have FTP enabled on your server, the folder structure of the ibay will be accessible that way too. It's not a huge concern for me at my workplace, (small shop), but if you are really security conscious, you may want to modify things to tighten it up a bit.