Hello,
I tryed to search the forum but haven't found this request - so if it is a duplicate please tell me.
At the moment it is not possible to add mail alias (e.g. to receive more than one mail address in one postbox). So the only possibility to acchieve that is to add a second one which is doing a redirect.
The redirect itsefl has a lot of problems for me about the spam fight. If it is a redirect address the Spamassassin (and I think Clamav too) plugin is not fired and in that case no spam check is done. As the redirect happens localy the mail is not checked for spam because it is a local address which is whitelisted. So all spam sent to "redirect_address@domain.tld" is never checked for spam. Just the normal server checks like DNSBL or Greylisings are done.
To avoid that the only possibility for me is to create a full mail address and create some sieve rules to redirect the mails. But this is a lot of work and on updating the RoundCube plugins it is going to be deactivated by default, so I have a little downtime from sieve and I have to recheck all the mail addresses. Last but not least I have to learn spam messages by logging into the mail account which receives the mail and redirects them using sieve. Because learning it in the main address would never apply on redirects. (Yes I know there is a domain wide spam blacklist database but I do not want to use it.)
In a perfect world 
:
- The possibility to add alias in the same domain.
- Link domains to be able to add alias accross domains.
but I was a little bit in hurry 