We have been migrating from Lotus Notes to Exchange.  We have also now been rolling out Enterprise Vault for archiving.  We set quotas in Exchange to 2.5 GB because we knew that until Vault was in place some of the migrated mailboxes with our new email policies would get larger than the 1 GB quotas we actually want to use.  Now we are getting to the point where we want to change the Exchange quotas back to 1 GB. 

1. If we lower quotas, the mailboxes that are over can't receive mail.  (we have as part of the Vault rules both age and quota based -to archive their mailboxes until available storage is 10% free)  But will Vault be able to archive mailboxes that are already over their Exchange quota?  I ask this because I know that someone had gone over the 2.5 GB limit and was not in a Vault provisioning group yet and I could not enable the mailbox in Vault...I had to delete some mail first to get it under the quota...then I was able to enable so it started archiving that night.  However, In the case of my question, the users would already be setup in Vault.