This is also a problem for me.

Zimbra is used on intranet with a domain.lan address. Internet emails are received by 2 different hosted mail domains: domain1.com and domain2.com.

I get all inbound emails delivered using fetchmail.

But, Outbound emails do require an internet-valid From address. I would expect that when a new mail is created, the From address would be the one selected in the user interface (Account). This is currently not the case (bug ?).

Running 5.0.21_FOSS_Centos5, the only way I found was to set the canonical Address as user1@domain1.com.

Would appreciate your comments. Thanks