FutureQuest, Inc. FutureQuest, Inc. FutureQuest, Inc.
Knowledgebase: Troubleshooting
Email bouncing due to unknown name?
Posted on 15 January 2004 06:03 AM

Question:

I have received a report from my client who is hosted by FutureQuest that several people have had their email bounce back when sent to his address:
myclient@example.com

I have no idea what the problem may be, as this domain has been active and working correctly for over a year.

I currently have "myclient" configured as a POP mailbox on the account, so there's no reason that people should be getting a "User Unknown" bounce error. Additionally, I have the "catch-all" alias enabled, so NO emails should be bouncing back to people.

I've received several of these emails over the past few weeks, which seems to coincide roughly with when the complaints of bounce backs came in.

----- The following addresses had permanent fatal errors -----
<myclient@example.com>
(expanded from: <myclient@example.com>)

----- Transcript of session follows -----
mail.local: unknown name: myclient
550 <myclient@example.com>... User unknown

Reporting-MTA: dns; mx1.example.com
Received-From-MTA: DNS; mx03.futurequest.net
Arrival-Date: Sat, 15 Nov 2003 20:30:44 -0800

Final-Recipient: RFC822; <myclient@example.com>
X-Actual-Recipient: RFC822; myclient@example.com
Action: failed
Status: 5.1.1
Last-Attempt-Date: Sat, 15 Nov 2003 20:30:44 -0800

Answer:

The information you've provided includes:
Reporting-MTA: dns; mx1.example.com
However, there is no such entry like that in our DNS system -- the MX record for 'example.com' is 'mx.futurequest.net'.

In addition, the FutureQuest mail servers use 'Qmail', and do not issue a 'user unknown' error message like the one you referenced:
mail.local: unknown name: myclient
550 <myclient@example.com>... User unknown

From the information you've provided and based on the items presented above as well as previous reports we've received that echo this scenario, I would guess that your client is using Mailwasher (http://www.mailwasher.net/) to 'wash' his email before downloading it. Mailwasher, a third-party mailcheck/spam blocker program, reportedly gives the user the option to bounce emails back to sender by creating a fake (although authentic-looking) "User Unknown" bounce message, then sending it back through either the sender's mail server or the user's depending on what's available.

I hope the above explains what you are seeing.