I am setting up mail server for 10K users. Here is what I have planned two incoming servers [zimbra-mta] two MBX Server with one as a LDAP Master and other will act as a LDAP Replica and two outgoing servers. Out of which Two incoming [MX records] willalso act as a IMAP Proxy. I will not be using SSL; it will purely be SMTP, IMAP, POP3. Now I would like to know how much RAM I would need for MBX servers?
Also, there might be a chances that management might not approve for distributed setup and I might need to setup one server only having all the roles installed at this moment. In this case how much RAM would you suggest and what should be the server size or parameters should be considered for server sizing.