I had a server running Zimbra 8.6 and it was configured to send via any one of five external relays based upon which one of my external accounts I was sending from. This worked great until I had a server crash and rebuilt this one using the latest Zimbra 8.7.
I have read and researched and tried everything I had done for my old 8.6 system and I simply cannot get this to work! When I try to send an email from the web client to gmail I get a warning from gmail that my server's IP address and domain are not allowed to relay since they are unauthenticated. According to my postfix configuration I should be authenticating using my own gmail credentials. But, the web client seems to ignore this.
When I try logging in directly on the Zimbra box I can use sendmail with the -tf parameters to mock up an email from one of my addresses to gmail and it works just fine. It is sent and looks like it came from the proper relay domain.
Is sender dependent relaying broken on 8.7? Does it work for anyone?
Welp, I gave up and set my server up to use gmail as the external relay for all accounts, and in my admin console I set my user account to be able to send from all of my external email addresses (specifying each of them there).
Now it properly relays through gmail and still shows each message as coming 'from' the external account I select in the new message window.
Maybe this will help someone with a similar issue.