LMTP with alias addresses

Hi, my problem is this: if i use lmtp for delivery and lookup for real_virtual_user@mydomain.com all function perfectly and mails are delivered correctly (quota and presence of user also)

but if i send an email to real_alias_address@mydomain.com LMTP service (it's an alias containing several users) dosen't find user. How can i resolve this problem? for completeness my system users is based on vpopmail userdb