Recipient email address is possibly incorrect on antispam gateway

Hi,
from the log it looks like the foreign mail system rejected your message but error message is common mesage.
Can turn on diagnostic log and give me SMTP transaction info for this message, please ?
In this log we can see real smtp To, what type of connection the servers negotiate and also reason of closing
transmission.

If your user is anything like my users, they have a bad address in autocomplete, but keep trying to use it... Then they try and blame it on the server...

On exchange smtp receive log, there is no entry for those missing emails.

On our Antispam gateway, only the following is logged.
"as1 postfix/smtpd[29111]: warning: proxy inet:127.0.0.1:10020 rejected "RCPT TO:<xxx@xxxx.com>": "554 Transaction failed"

Can Exchange smtp log can record all incoming connection, not match it is success or fail ?

Thx

SO as I understand now you have internal Exchange server which deliver messages to your mail gateway.
The error message is on this mail gateway and the flow of the message is Exchange server -> mail gateway -> foreign system.
On mail gateway the system is receiving message from Exchange on some port, then internal flow on mail gateway
between smtp server and antispam engine and than final delivery out. It looks like (based on port 127.0.0.1 which is local loopback address) the problem could be internal in mail gateway.
Turn on diagnostics logging of SMTP server in Exchange - http://exchangepedia.com/2007/05/exchange-server-2007-logging-smtp-protocol-activity.html to be sure the e-mail address and other part of transmission are OK.
Next step will depend on result - Exchange server issue or mail gateway issue.

The problem is on the incoming emails.

Sender -> Anti-spam gateway --> Exchange 2010

SMTP log for receiving has been turned on. However, missing emails can be shown on the log.

Thx

Does your gateway have some sort of user verification?
Mine uses LDAP to look up users before passing on the mail... Could yours have a manually created list that isn't getting updated? Or one created by a cron job that is failing to update?

No such setup.

Actually, can LDAP vertify incoming sender from public internet ? Only sender with my home domain should check LDAP, Otherwise, it shoudln't or it will block other domains to pass through, correct ?

Thx

Actually there are filters that do "callback" verification, but it is a depreciated practice if I remember correctly.

Also some filters will verify if a senders domain has a valid MX address, some will verify other aspects of the sender.

So these are messages coming into your organization, and getting stopped at the filter? Or they make it to the exchange server and then disappear?

Bypass the gateway and all mails can deliver to Exchange within missing. Already reported to vendor but seem like it takes time to resolve...  They are still investigating.

Is there any apps that can accept mails and a decision to route to diferent hop based on email domain ? They may be a quick temporary solutoin.

Thx

OK, it is possible to turn on temporary debug logging on IMSVA (Logs\Settings - Log Files - Application log detail level - DEBUG)
and ask your partner to send the same problematic message again, please ?

The setting was setup to DEBUG.

How to get the log for investigation ?

Thx