suppose i've got a domain example.com in zimbra and would like to add an email address x@example.com for which i'd like to accept mails, but don't store localy the incoming emails just forward to another address x@another.com. how can i do that? we try to add an account x in example.com, the add a forwarding address x@another.com and in x's preferences we try to set "Don't keep a local copy of messages". it seems to working i.e. sending a mail from sender@example.com to x@example.com, then x@another.com got the mail and the mail is not stored in x@example.com.
BUT the sender@example.com who send the original mail got back a message from zimbra's postmaster as "Mail Delivery System <MAILER-DAEMON@example.com>".
why? how can i fix it? and what is the right way to do so?
thanks in advance.
yours.

in maillog we see this:
May 4 13:27:52 server postfix/smtpd[28264]: initializing the server-side TLS engine
May 4 13:27:52 server postfix/smtpd[28264]: connect from server.example.com[192.168.1.3]
May 4 13:27:53 server postfix/smtpd[28264]: 1BC7C6EC0698: client=server.example.com[192.168.1.3]
May 4 13:27:53 server postfix/cleanup[28268]: 1BC7C6EC0698: message-id=<15747292.31146742072030.JavaMail.root@server.e xample.com>
May 4 13:27:53 server postfix/qmgr[5559]: 1BC7C6EC0698: from=<sender@example.com>, size=497, nrcpt=2 (queue active)
May 4 13:27:53 server postfix/smtpd[28264]: disconnect from server.example.com[192.168.1.3]
May 4 13:28:03 server postfix/smtpd[28323]: initializing the server-side TLS engine
May 4 13:28:03 server postfix/smtpd[28323]: connect from localhost[127.0.0.1]
May 4 13:28:03 server postfix/smtpd[28323]: 773176EC06AD: client=localhost[127.0.0.1]
May 4 13:28:03 server postfix/cleanup[28268]: 773176EC06AD: message-id=<15747292.31146742072030.JavaMail.root@server.e xample.com>
May 4 13:28:03 server postfix/smtpd[28323]: disconnect from localhost[127.0.0.1]
May 4 13:28:03 server postfix/qmgr[5559]: 773176EC06AD: from=<sender@example.com>, size=1240, nrcpt=2 (queue active)
May 4 13:28:03 server postfix/smtp[28336]: 773176EC06AD: to=<x@another.com>, relay=sender.example.com[192.168.0.1], delay=0, status=sent (250 Ok: queued as
C7BEA37654A)
May 4 13:28:03 server postfix/error[28335]: 773176EC06AD: to=<x@example.com>, relay=none, delay=0, status=bounced (example.com)
May 4 13:28:04 server postfix/cleanup[28268]: 0065A6EC06AF: message-id=<20060504112804.0065A6EC06AF@server.example.com >
May 4 13:28:04 server postfix/qmgr[5559]: 0065A6EC06AF: from=<>, size=2822, nrcpt=1 (queue active)
May 4 13:28:04 server postfix/qmgr[5559]: 773176EC06AD: removed
May 4 13:28:04 server postfix/smtp[28269]: 1BC7C6EC0698: to=<x@another.com>, orig_to=<x@example.com>, relay=127.0.0.1[127.0.0.1], delay=11, status=sent (250 2.6.0 Ok, id=04341-01, from MTA([127.0.0.1]:10025): 250 Ok: queued as 773176EC06AD)
May 4 13:28:04 server postfix/smtp[28269]: 1BC7C6EC0698: to=<x@example.com>, relay=127.0.0.1[127.0.0.1], delay=11, status=sent (250 2.6.0 Ok, id=04341-01, from MTA([127.0.0.1]:10025): 250 Ok: queued as 773176EC06AD)
May 4 13:28:04 server postfix/qmgr[5559]: 1BC7C6EC0698: removed
May 4 13:28:04 server postfix/lmtp[28348]: 0065A6EC06AF: to=<sender@example.com>, relay=server.example.com[192.168.1.3], delay=0, status=sent (250 2.1.5 OK)
May 4 13:28:04 server postfix/qmgr[5559]: 0065A6EC06AF: removed