Multiple email addresses +Postfix

["Stelios A." <stelios.a@gmail.com>]

Hello all,

I have a master/slave Openldap 2.4.9 running on ubuntu server along
with Postfix and dovecot.
At the moment email server is able to server email for domain1.com
with Maildir support for Dovecot at /home/username/ for each user.
There is a need to add a 2nd domain let's say domain2.com.
My question is where that domain will store the emails as the user
home dir is already setup in ldap at /home/username
Is there a way to define a new attribute like alternative email and
have the same user with same auth details authenticate to both domains
like user1@domain1.com and with same pass on user1@domain2.com?

I'm not sure if I'm explain enough the situation, please ask for any
clarification if you want to.

-- 
Stelios A