Limitation of open source(free version)

[Shikha Sood]

Hi
I want to use ZCS(open source free version) .
I was wondering if there are any limitations such as
1. Number of user accounts that can be made?
2. Maximum Size of mailbox?
3. If attachements are allowed? If yes what is the maximum size?
4. Can the mails be sent to an external mail box? like yahoo., gmail or any other corporate email id?

[Dirk]

No limit on mailbox quantity
No limit to mailbox size
Admin configurable attachment size
emails can be sent to any email address