Don't know if this is a Beta Support or standard mailtraq support question, but I'll post here since I'm using Build 2818. Standard (non-ewa) Webmail.
Twice now in the last week, I've had posts turn up at recipients' mailboxes that have been completely blank.
The first had little in it that I thought important, but the second had more than an hour's considered reply, and the disturbing thing was that the original didn't appear in the either Sent Mail or Drafts (ie I lost it all). Now I was able to recreate the mail from what I remembered typing, pasting, and making up, but it was quite disturbing to have NO record at my end.
In the log, it's transmission was logged as follows:
00001000 00001A4C 11/03/2010 12:16:46 HTTP: Accepting connection from 192.168.0.106
00000080 00000000 11/03/2010 12:17:00 Routing (Inbound) HLLVBD4C8600 (1 locked, 0 queued)
00000080 00000000 11/03/2010 12:17:00 Router: (Depth 0) HLLVBD4C8602 from andrew@****vet.com.au for (4 rcpts) helen@****vet.com.au,lesa@****vet.com.au,jim@****vet.com.au,kate@****vet.com.au
00000080 00000000 11/03/2010 12:17:00 Router: Storing HLLVBD4C8602
00000080 00000000 11/03/2010 12:17:02 Router: Storing HLLVBD4C8602
00000080 00000000 11/03/2010 12:17:03 Router: Storing HLLVBD4C8602
00000080 00000000 11/03/2010 12:17:05 Router: Storing HLLVBD4C8602
00000080 00000000 11/03/2010 12:17:06 Routing (Inbound) completed late HLLVBD4C8600
So it thought it sent something.
The header of the emails they received looked okay. It's just that the body had completely disappeared.
Like the previous one that arrived blank, it was a Reply All, and also was probably auto-saved more than once.
I'm pretty certain that I didn't do Select All, Delete just before sending, and that still doesn't explain the fact that there is nothing in my mailslot that resembles my message around that time.
Anyone seen this sort of behaviour, or am I special?
:-)

I've not seen this behaviour myself. How often was it auto-saved? Generally if I spend a long time composing anything on a web page I tend to copy to the clipboard before posting, which is probably a good habit until we can figure out what is happening. In Standard WebMail pretty much everything is stored in the session, but the auto-save feature should ensure the session doesn't get disconnected. Perhaps more importantly, Standard WebMail only has one session per cookie, so if you compose a second e-mail while still composing the first, it is possible to close the first session data. Could that have happened? EWA has the advantage of putting much less data in the session.
Yes, it could indeed have been a multiple-sending issue. When I compile huge replies, I tend to get distracted into other replies as other stuff comes in.
So it could well have been this.
Will the "future webmail client" be more robust in this behaviour?
I don't think you're "special" in this regard. I have experienced it myself. It started in the last few months and my users are sporadically complaining about it. This issue happens on Replies and Forwards. The behavior is exactly as you describe. Blank email delivered and no record of it in the Sent items folder.