What do I need to do before my account migrates?

There are a number of things users should do in advance of their account being migrated to Office 365. The information on this page describes actions to take to ensure optimal results.
E-mail
Please review the contents of your Mailbox and folders to find received and sent items that are no longer needed. Removing these items from the account will help your Office 365 begin with less clutter, and can help your account migrate more quickly.
As messages larger than 25 megabytes in size will not migrate to the new system, we recommend using the information at the following two links to locate any messages you may have of this size and store them outside:
Seeking messages 25 Megabytes or larger:
https://mail.google.com/mail/u/0/#search/size%3A25000000
Overall Account Size
After you have done your account cleanup and either saved to disk or deleted messages in your account or archive that are larger than 25 MB, it is worth looking at the overall size of what remains. We think that there are very few, if any, people for whom this will be an issue, but if the total content moving from Google Apps to Office 365 amounts to more than 25 GB, then the consequences would be serious. Migration of your Google Apps content would be incomplete and you would be unable to send or receive messages in Office 365 until your account size is brought below 25 GB.
To forestall such a calamity, please check the size of your account. You find size of your mailbox by scrolling all the way down to the bottom of your mailbox. You should see something like this
[box style=”1″]Mobile Devices
Smartphones and tablets using Google Apps (gmail) should have a relatively-simply migration process involving the deletion of the existing account and addition of the new one. The Office 365 Mobility page has details on configuring your device to the new system when the time comes.
If your device synchronizes to a Google Apps (gmail) contacts and you sometimes populate fields such as Birthday, you may wish to consider exporting your Google Apps (gmail) contacts prior to migration. This will help ensure a copy of this information is kept in case some fields do not migrate.
Google Apps (Gmail) Filters
Unfortunately, there are no options to automatically migrate your Google Apps (gmail) filters. Those who have Google Apps (gmail) filters need to document them prior to migration in order to preserve the workflow and create similar ones in Office365. This link explains how to go about it.
Google Contacts
Contacts will not migrate to Office365.
To help ensure that nothing is lost from contacts, we suggest exporting a copy to a .CSV file, which can be opened in Excel. Click here for detailed instructions.
You can then use the information given here to import the .CSV file in to Office 365