IMAP integration questions

IMAP integration questions

Hi, I had a few questions about Office 365 IMAP integration:
  1. Do emails (and their attachments) count against your storage?
  2. Is it correct to assume when a user leave the company and you deactivate their Exchange account, this will also remove their synced emails?  Any way to retain them?  I feel they would be valuable communications to retain with records.
  3. Privacy: I know it varies company to company, but generally speaking what is the industry standard in the US for email sharing permissions: private or public?  Again I feel like public would be of more value but I'm wary of enabling this with existing users and exposing prior emails.
Thank you.