From: Salim-SESO on

We are running exchange 2003 server and recently found that when email send
to large distrubution group with attachement it failes for good number of
usersand some time MTA service in stopped stage and had to start it manually.
Also following event will be logged on the server.

Event Type: Warning
Event Source: MSExchangeMTA
Event Category: X.400 Service
Event ID: 290
Date: 5/10/2010
Time: 10:31:01 PM
User: N/A
Computer: MAIL02
A non-delivery report (reason code unable-to-transfer and diagnostic code
unrecognised-OR-name) is being generated for message C=us;A=
;P=it;L=MAIL02-100510161721Z-10265. It was originally destined for
number 1), and was to be redirected to . [MTA DISP:RESULT 16 136] (12)

So which part i have to check first t resolve this issue.