Welcome to the forums,
I assume you meant 'converastion' view and not 'collaboration' view:
If your talking about little plus symbols in mail view to expand threads-this is comming in v5-check out the beta!
It's already been in the
Zdesktop(alpha release) client for some time. (Previously named hybrid view in 0.38, now it's just incorporated into conversation view.)
Someone want to show her a pic of their v5beta2 or their Zdesktop?
Shared mail folders is also in the v5 beta! Just like you would right click to share a calendar/addressbook/documents-works pretty nice.
For intergration with NNTP:
Bug 17715 - Allow reading of/posting to newsgroups (NNTP/Usenet)
"easy archieving/migration" For compliance purposes:
Archiving & Discovery
There are multiple migration tools for outlook PST's/Groupwise/Exchange. Comming from Syrus? -imapsync will be your friend
In the network edition there's Hierarchical Storage Management (HSM) which allows you to configure storage volumes for older messages. To manage your email storage resources, you can implement a different HSM policy for each message server. Messages and attachments are moved from a primary volume to the current secondary volume based on the age of the message. Thereby moving older messages and data to less expensive disk storage.
Compare features in the OS vs NE editions
There are also a few things in the works for enhanced file management
