Comment ISPMAN (Score 1) 1216
I think the best Open Source solution is ISPMAN.
It uses LDAP as it's backend database and is all-in-one ISP solution with mail+web+dns+etc. You don't have to use everything if you want.
The best thing is that "you may start with a single server to manage user's mailboxes and add more as you grow. ISPMan can manage this and allow you to create user's accounts and mailboxes on different servers. This does not affect the user at all but allows the system administrator to balance the load of mails on different machines."
It uses LDAP as it's backend database and is all-in-one ISP solution with mail+web+dns+etc. You don't have to use everything if you want.
The best thing is that "you may start with a single server to manage user's mailboxes and add more as you grow. ISPMan can manage this and allow you to create user's accounts and mailboxes on different servers. This does not affect the user at all but allows the system administrator to balance the load of mails on different machines."
