[deanhills]

Generally a dead.letter file is created when a mail server or mail client isn't able to send out mails for some reason (server errors, non existing e-mail inboxes, etc...).

To stop it from being created you have to find the root cause.

Thanks for the explanation @"Hidden Refuge"  It's a communication happening at the root level by root to root. Still have to figure out the cause.

I'll check later tonight to see whether the file has increased in size. After my research last night I was reasonably happy that it wasn't due to VestaCP hacking and then restarted VestaCP successfully.  Everything that I worked on was perfect with great speed - wow I was impressed!  No strange files or anything.  Except I'd mentioned the dead.file to Hostus.us as well, and they then pointed me in the direction of another thread that had been posted at VestaCP about a hacking.

I feel really sorry for VestaCP as they don't seem to be able to get away from the major exploit in April.  So if someone opens a thread that his VPS has been hacked, everyone runs for cover and the VPS hosts get nervous.  I was cautious however in stopping the VestaCP panel after I had done everything I needed to do, but am almost certain this wasn't a VestaCP problem but an inexperienced and chaotic user who hadn't updated his VestaCP.  His last update predated the April fiasco.