CentOS team... as is already bug reported and marked solved... as we await the upstream repair for this.
It was reported that this was happening on CentOS 5. You likely already know, but it also happens on CentOS 4.
For those unaware. It seems that SquirrelMail has an issue which allows mail to be sent out from one user on the system and it uses the from address of another user on the system. Apparently, both users need to be logged into SM at the same time.
My client reported that when he sent the affected message, he received a connection lost notice. He logged in again, stated that the email was in fact sent. The recipient of that email asked what was up with the odd from address. Looking at the headers from that message, they do in fact show adifferentusername@thisparticularservername.com.
This is about the most embarrassing thing that's ever happened with my servers. Obviously the affected user is not feeling very secure. It does invite the recipient to reply to the wrong address which could be bad on so many levels (imagine having a few local law firms hosted on the same server?). I view this as a horrid security issue. If maybe the CentOS team might be so kind as to push the SquirrelMail update to the front when it's ready, that would be greatly appreciated.
John Hinton