Creation of a mail service. On what can all this be lifted?

Question

Mail server

There was a task on creation of a mail server. The approximate number of users is up to 100,000 people. Now the question arose on what and how to implement and how to choose the architecture (hardware, software)?
It is desirable to use on open-source, without any closed software. Should I use virtualization or do it on bare iron? It is necessary to do everything taking into account the growth or decrease in the number of users (i.e. automatically turn off and turn on equipment or virtual machines).

Answer 1

Konstantin Berezov @Berezoff
Zimbra should suit you. And you definitely need virtualization - as a means of expansion and scalability (in my opinion, the VMware platform is best suited for this - even though it is paid. It’s better not to save on this) and more memory, since Zimbra loves to eat RAM. The calculation is approximately the same for 100 mail accounts, you need 6 GB of RAM.
I also recommend taking a good mid-level storage system with FC - and placing virtual machine files on it. It is advisable to bribe a shelf with capacious SATA disks for backups to the storage system. Well, later, if necessary, then buy a tape backup.

Answer 2

Service SFLetter.com is made on Roundcube - you can see how it looks "live"