On Thu, 26 Sep 2002 [log in to unmask] wrote:

+ Given that Hotmail usually reports *other* 5xx errors with a fairly good
+ explanatory text like "over quota" or "deactivated user" and so on, the
+ current spate of '5xx Transaction Failed' sounds like plain crack-induced
+ bogosity - especially in conjunction with all the connection reset and
+ refused errors I'm seeing.

Or as found through Google at
http://www.freelists.org/archives/freelists-users/09-2002/msg00016.html

"
 The "transaction failed" message is apparently a "we're too busy to
 accept your message at the moment," which is fine, but they should fail
 with a 4xx message, for example the 450 "mailbox unavailable."
 Microsoft, in their infinite wisdom, has decided to not follow RFC here
 and is instead sending a 554, causing mail to bounce permanently.
"

As always with things found on the web, no idea about the validity of this
statement.
--
Xander