Several key factors must be addressed when planning the migration to Exchange Online to ensure it is done successfully. These are both technical factors and human factors.
There are numerous technical considerations that must be taken into account when planning for a migration. Some of the more common questions are as follows:
Which of the previous example scenarios mirrors yours?
Have users been informed of the change?
How much data can you send through your Internet link to Exchange Online (meaning how many gigabytes of mail can be uploaded)?
Does your monthly Internet download allowance cater for the mailboxes being downloaded back into the Outlook OST file for each user?
Do you plan to start users on Exchange Online with their full mailbox or just a portion of recent content?
Do you have access to all desktops so you can configure the new account in Outlook?
How many computers will you have to re-configure, and do you have the resources to do them...