[Dovecot] OT: Large corporate email systems - Exchange vs open source *nix based

[Charles Marcus]

Hello,

There has been some whispers about considering migrating our mail 
systems to Exchange Server. I want to try to nip this in the bud.

I would like to ask for some help with providing some kind of comparison 
of large(r) commercial companies use of email systems... specifically, 
those using Microsoft Exchange Server, vs those using open source 
Linux/Unix based systems, including even commercial *nix groupware based 
systems like Zimbra, as well as plain mail systems like dovecot, or 
cyrus or courier.

I know that many (if they are smart) Admins that do use Exchange 
internally will use postfix (or something else linux/unix based) in 
front of it as their relayhost (for both inbound and outbound), so just 
counting the number of publicly accessible smtp servers won't be a good 
gauge.

Does anyone know of any decent non-biased studies that have been done, 
hopefully relatively recently (last few years) that provide such a 
comparison?

Thanks,

-- 

Best regards,

*/Charles/*