In ISPConfig 2 there was a little nice feature for mail user where you could easily forward mail to another mail address, with or without leaving a copy on server:
It was really useful feature because user could always forward mail and leave a copy (or not) on server with single click. ISPConfig 3 does not have that feature (well, it has, but you can’t easily select to keep copy or not) but it has custom for mailbox where you can define filter using Sieve.
To forward mail to another mail address with keeping copy on server, in custom rules enter:
To forward mail to another mail address without keeping copy on server, in custom rules enter:
redirect “email@example.com”; stop;
stop; is really significant in this rule because ISPConfig 3 automatically adds keep; to end of every Sieve custom rule and stop; stops further Sieve processing. Without stop; rule forward mail and keeps it on server.