issues with 400GB account?

[1415bhwong]

We have an archive account where some of the emails sent and received will get bcc into this account thru postfix sender_bcc and recipient_bcc configuration.
This account is reaching 400GB and today, all incoming email suddenly stop coming in and jam at the email queue. The error message is:
Reason: delivery temporarily suspended: conversation with domain.com timed out while sending end of data - message may be sent more than once.
I attempt to create a new archive account and amend postfix sender_bcc and recipient_bcc configuration accordingly. However, when I attempt to update Zimbra on the new configuration by executing:
postmap /opt/zimbra/postfix/conf/sender_bcc
I get this error:
open /opt/zimbra/postfix/conf/sender_bcc.db: Permission denied
So I tried the next best option, rename the current archive account and create a new account using the original name. This resolve the incoming email issue. However, is it possible to recover the original corrupted archive account?
Question 1: Is there a size limits for zimbra account?
Question 2: Can I recover this account from Zimbra Backup without getting my 50GB temp folder consumed? I asked this because I realize that moving or restoring huge amount of email will consume huge amount of temp storage. And when temp storage get to zero, Zimbra will stop working. Is there anyway not to let Zimbra use up all the temp storage when doing such task?