Sorry for the title, I don't know how to sum up this situation.

I have a web server at mydomain.com, running qmail for website related mail delivery (i.e. newsletter, sign up confirmation, etc). qmail here is used only to send mails, because I have a fully working Google App Gmail associated with mydomain.com for normal email receiving.

qmail runs fine when sending email to remote addresses, for example to [email protected], but fails when sending to [email protected]. I think it's because the server thinks that he have to manage mailboxes for mydomain.com locally, instead of redirect them to Gmail. Here is the /var/log/qmail/current for two email: the first one is sent without problems to example.com, second one fails because it's for mydomain.com:

2012-11-15 15:04:11.551933500 new msg 262580
2012-11-15 15:04:11.551936500 info msg 262580: bytes 5604 from <[email protected]> qp 5185 uid 33
2012-11-15 15:04:11.575910500 starting delivery 316: msg 262580 to remote [email protected]
2012-11-15 15:04:11.575912500 status: local 0/10 remote 1/20
2012-11-15 15:04:12.189828500 delivery 316: success: 74.125.136.27_accepted_message./Remote_host_said:_250_2.0.0_OK_1352991894_j49si13055539eep.9/
2012-11-15 15:04:12.189830500 status: local 0/10 remote 0/20
2012-11-15 15:04:12.189831500 end msg 262580

2012-11-15 16:49:20.270332500 new msg 262580
2012-11-15 16:49:20.270336500 info msg 262580: bytes 2192 from <[email protected]> qp 5479 uid 33
2012-11-15 16:49:20.315125500 starting delivery 323: msg 262580 to local [email protected]
2012-11-15 16:49:20.315128500 status: local 1/10 remote 0/20
2012-11-15 16:49:20.320855500 delivery 323: failure: Sorry,_no_mailbox_here_by_that_name._(#5.1.1)/
2012-11-15 16:49:20.320858500 status: local 0/10 remote 0/20
2012-11-15 16:49:20.372911500 bounce msg 262580 qp 5484
2012-11-15 16:49:20.372914500 end msg 262580

As you can see, it says:

Sorry,_no_mailbox_here_by_that_name

I can't say he's wrong :)

How to solve this? How to let Google App Gmail manage incoming email for mydomain.com for messages sent by mydomain.com qmail server?