Regarding the attachments - I see two issues here. 1) Deleteing an attachment from a received message; and 2) having it stored somewhere else.
Issue 1 has been addressed in
bug 233 - Ability to remove attachment from received message, which will be available in the next release - ZCS 6.0.2.
As for your second issue, this is not currently supported. A
workaround for this would be to use the Briefcase feature. A user can save attachments to the briefcase and
then delete the attachment from the message (as above - from 6.0.2 onwards). The briefcase can be shared and accessed via HTTP.