Office 365

Migration Preparation

Once your migration date has been set, you will want to make sure you are ready for the move. Most of the work of the migration is done by the IT staff, but there are some things that you can do to make sure that your migration goes smoothly.

Locate and export large emails and attachments

Emails and attachments larger than 25 MB cannot be migrated, and must be either saved outside your mailbox, or deleted. If you do not remove these items prior to the migration, we will export them to a .pst file for you.

In most cases, messages are large because of attached files. If there are large attachments on messages in your Sent Items folder, you probably already have the original document saved on local storage.

Follow the instructions in the links below to locate all messages over 25 MB in your mailbox. Then you will need to review the messages and decide whether to permanently delete the message and any attachments, or to save them to local storage outside of your mailbox.

Handling large messages in Outlook 2010

Calendar/Mailbox delegates must be migrated together

If you have a delegate, or you are a delegate on someone else's calendar, and they are not included in this migration, please notify the staff handling your migration.

Cached Mode 

If you are running your Outlook client in cached mode, it is best to turn off cached mode prior to the migration. Once you are migrated, you can go back to cached mode if you prefer.  If you need assistance in determining whether or not you are running Outlook in cached mode, please contact the IT Help Desk.

Timing of your migration

Although the command to finalize the migration is scheduled to run at a particular time, it may take several hours to complete. An exact time for the completion of your migration cannot be determined.  You will be able to continue to use your mailbox during the migration.

Once your mailbox migration is completed, you will lose your connection, and will need to close/reopen your client. In some cases you will need to change your client settings. It may take 15-20 minutes before you are able to reopen your Outlook client.  If you need immediate access, OWA will usually allow access immediately after the migration completes.

Client configuration instructions for a wide variety of clients and devices can be found on this website, under Client Configuration on the left side-bar.

Large Mailings

Office 365 includes some security defenses that limit the ability of an individual to send huge numbers of messages in a short amount of time. If you have legitimate large mailings to do, please understand these limits and the alternatives you have for delivering your messages.

• The maximum number of addresses allowed in the To:, Cc:, and Bcc: fields is 500 per message.
• The maximum number of messages that can be sent from your email client is 30 per minute.
• The maximum number of recipients that can receive messages sent from your account (or an Exchange Group Account) in a 24-hour period is 10,000.


• It doesn't matter whether the recipients are at the University or elsewhere.
• The 24-hour period is a rolling window: for example, if you send messages to 2,000 recipients at 8:30 am, then messages to 5,000 recipients at 12 noon, then messages to 2,000 recipients at 2:30 pm, and messages to 1,000 recipients at 4 pm, you won't be able to send any more messages until 8:30 am the next day.
• If you try to send a message after exceeding the limit, you will either see an immediate error about the recipient limit, or the message will be returned to you with an error. Save the message to your Drafts folder and try again later.
• A message will only be delivered if it can be delivered to all the recipients without going over the 10,000-limit. For example, if you've already sent messages to 9,900 recipients, and you attempt to send one message to 150 recipients, it will not be delivered to any of the recipients because it would be 50 recipients over your limit for the 24-hour period.

See Microsoft's detailed explanation of message and recipient limits

Suggested Alternatives

If you expect to email the same group of recipient multiple times, and the list of recipients includes addresses both internal and external to USF, a listserv is an excellent alternative. If the list of recipients are all internal to USF ( or email addresses), a distribution group can be created to meet your needs. IT can help you create a listserv or a distribution group. Please contact the IT Help Desk for assistance.