LDAP schema shipped in iRedMail-0.4.0 and prevous version don't have objectclass for mail alias, but you can use the current version:
http://iredmail.googlecode.com/svn/trun … ail.schema
It should work if you replace the old schema file by the new one, no extra migration steps required.
It has 'mailAlias' objectclass:
objectclass ( 1.3.6.1.4.1.32349.1.2.4.4 NAME 'mailAlias'
DESC 'Mail Alias' SUP top STRUCTURAL
MUST ( mail $ mailForwardingAddress )
MAY ( enabledService $ accountStatus $ description $ cn ))
Example ldif:
dn: mail=all@a.cn,ou=Aliases,domainName=a.cn,o=domains,dc=iredmail,dc=org
objectClass: mailAlias
objectClass: top
mail: all@a.cn
accountStatus: active
mailForwardingAddress: user1@a.cn
mailForwardingAddress: user2@a.cn
mailForwardingAddress: user3@a.cn
mailForwardingAddress: user4@a.cn
description: mail alias for all users
enabledService: mail
enabledService: deliver
enabledService: forward