In previous OS X Server versions there was a GUI setting which allowed you to “Copy all mail to…” an email address of your choice. It does not exist anymore, but you can still set this parameter by using the command line:

sudo serveradmin settings mail:imap:postmaster_address = "myemailaddress@mydomain.tld"

sudo serveradmin settings mail:postfix:always_bcc_enabled = yes 

Make sure you change myemailaddress@mydomain.tld to the actual email address you’d like to bcc.

If for some reason the always_bcc_enabled setting does not change, it means that most likely serveradmin got stuck and you need to do some manual editing of:

/Library/Server/Mail/Config/postfix/main.cf

and change the line that starts with:

always_bcc =

to:

always_bcc = myemailaddress@mydomain.tld

After that, try the serveradmin commands again.

Besides above commands, there are many more parameters that can be set via the command line. For an overview, issue:

sudo serveradmin settings mail

Be careful when unsure about changing a parameter and always make sure you have a working backup.