Postfix: Transport for Email Forwarding

I've a Postfix setup with virtual users running just fine. Some of my users redirect their email to external email gmail accounts, for example: [email protected] is forwarded to [email protected] for their own convenience via virtual_alias_maps.

Now I tried to use transport_maps to have a dedicated transport for those forwardings like so:

main.cf:

virtual_transport = lmtp:unix:private/dovecot-lmtp virtual_alias_maps = mysql:/etc/postfix/virtual/mysql-alias-maps.cf virtual_mailbox_domains = mysql:/etc/postfix/virtual/mysql-mailbox-domains.cf virtual_mailbox_maps = mysql:/etc/postfix/virtual/mysql-mailbox-maps.cf default_transport = out-default transport_maps = mysql:/etc/postfix/virtual/mysql-transport-maps.cf 

master.cf:

out-default unix - - n - - smtp -o proxy_interfaces=$smtp_default_transport_proxy_interface -o smtp_bind_address=$smtp_default_transport_interfaces -o inet_interfaces=$smtp_default_transport_interfaces -o myhostname=$smtp_default_transport_hostname -o smtp_helo_name=$smtp_default_transport_hostname -o syslog_name=smtp-$smtp_default_transport_hostname out-fwd unix - - n - - smtp -o proxy_interfaces=$smtp_default_transport_proxy_interface -o smtp_bind_address=$smtp_default_transport_interfaces -o inet_interfaces=$smtp_default_transport_interfaces -o myhostname=$smtp_default_transport_hostname -o smtp_helo_name=$smtp_default_transport_hostname -o syslog_name=smtp-fwd-$smtp_default_transport_hostname -o bounce_queue_lifetime=0 -o maximal_queue_lifetime=0 

mysql-alias-maps.cf:

query = SELECT destination FROM `aliases` WHERE source='%s' 

mysql-transport-maps.cf:

query = SELECT IF (ISNULL(destination), NULL, 'out-fwd') as transport \ FROM `aliases` \ WHERE destination='%s' \ AND destination LIKE '%%@gmail.com' 

What I'm trying to accomplish is "if the user has their email forwarded to a @gmail reduce the queue lifetime."

Now when I try to send and email to those users this is what happens:

postfix/qmgr[28839]: warning: connect to transport private/out-fwd,out-fwd: No such file or directory 

private/out-fwd,out-fwd > Why is it duplicating the name of the transport?

If I change the query to return out-fwd: (colon at the end) I get:

smtp-fwd-xxxx/smtp[23429]: fatal: valid hostname or network address required in server description: ,out-fwd: 

,out-fwd: ??? Why?

Note that if I simply comment the transport_maps line email gets delivered using default_transport = out-default just fine.

Thank you.