“I have been at my company for a long time and my mail box is huge. Will all my old messages be moved over?”
SHORT ANSWER: Yes :)
CUTOVER DAY: Once the cutover goes through, remember to go to mail.google.com from now on to check email. All your old emails will be moved here. Note that the cutover can take up to 24 hours so you'll want to continue checking your Outlook as well as your gmail for an extra day. Usually the cutover takes about an hour but may take longer for larger inboxes.
LARGE INBOXES: Everything will get moved. If a user has over 30gb of data (rare) then we'll increase their storage to 100gb for an extra $2/mo.