Looks like this does not work!
Nov 19 15:02:18 lt postfix/smtp[22046]: BB1A395: to=users@lists.roundcube.net, relay=ext-mx02.kolabsys.com[94.230.208.222]:25, delay=0.16, delays=0.06/0.01/0.07/0.02, dsn=5.7.1, STATUS=BOUNCED (HOST EXT-MX02.KOLABSYS.COM[94.230.208.222] SAID: 553 5.7.1 USERS@LISTS.ROUNDCUBE.NET: SENDER ADDRESS REJECTED: NOT LOGGED IN (IN REPLY TO RCPT TO COMMAND))