Office 365, Email, Migration, FAQ

FAQs for 2018 Exchange email migration to Office 365.

Are the URLs changing? 

Yes.  Mail clients made by Microsoft will try to detect the mailbox move and use the autodiscover process to automatically reconfigure the client with the correct URLs after it has been closed and re-opened.  The mail URLs are listed below:

Outlook on the Web:
Exchange Web Services:
IMAP: on port 143 TLS/STARTTLS
SMTP: on port 587 TLS

Will I need to reconfigure my mail client? 

Mail clients made by Microsoft will try to detect the mailbox move and use the autodiscover process to automatically reconfigure the client correctly after it has been closed and re-opened.  Any client not made by Microsoft will probably need to be reconfigured.

When will new mailboxes be created on Exchange Online instead of Exchange 2010? 

Beginning on 8/14/18 all new mailboxes will be created on Exchange Online. The Partner Computing service is no longer used to provision new Exchange accounts. For individuals who are new to the university, Exchange Online accounts are automatically provisioned based on eligibility data provided by BANNER. 

What about ADTools? 

ADTools will be updated to provide support for Exchange Online. 

When will I or my unit get moved to Exchange Online? 

The open call for mailbox migrations started May 1. Our target completion date is October 31, 2018. IT Pros should follow the process in this KB article to submit migration requests for their unit to

What about retirees? 

Retirees will be targeted directly later in the migration but you can include them in your unit migration if you already providing them with support. 

What about undergraduate students? 

Undergraduate students will start having new mailboxes created on Exchange Online instead of Google Apps in Fall 2018.  We will not be migrating any current Google Apps mailboxes to Exchange Online. 

How many mailboxes can be moved at a time and how long will it take? 

There are many factors that determine how many mailboxes can move at once and the speed at which the copy process happens.  We ask that moves be scheduled at least 4 days in advance to ensure we can accommodate for everyone.  

Our local Exchange is currently configured to support a maximum of 320 simultaneous active mailbox moves.  The number of items, folders, and mailbox size are the biggest factors on performance from our environment.  From the Microsoft side the biggest factor is how many moves they are processing from other customers.  Thursday through Sunday are their busiest days for on boarding and Monday through Wednesday are their lightest days. 

What new limits are introduced with Exchange Online? 

  • 100 GB mailbox quotas for users 
  • 50 GB mailbox quotas for unified groups 
  • Maximum number of messages per mailbox folder: 1 million 
  • Maximum number of messages per folder in the Recoverable Items folder: 3 million 
  • Storage quota for Recoverable Items folder: 100 GB 
  • Maximum number of subfolders per mailbox: 10,000 
  • Maximum folder hierarchy depth: 300 
  • Message size limit: 100 MB 
  • Subject length limit: 255 characters 
  • File attachments per message limit: 250 
  • Messages received: 3,600 per hour 
  • Recipient rate limit: 10,000 recipients per day 
  • Recipient limit: 500 per message 
  • Message rate limit (SMTP client submission only): 30 messages per minute 
  • Maximum number of distribution group members: 50,000 
  • Maximum message size for large distribution groups (>5,000 members): 2 MB 
  • Exchange ActiveSync device limit: 100 
  • Exchange ActiveSync file attachment limit: 25 MB
  • max concurrent connections per mailbox limit: 3
  • Junk Email folder retention period: 30 days

Who do I contact to get more information? 

The Technology Services Exchange Team is comprised of Joshua Mickle (jmickle), Bobbi Hardy (battleso), and Lee Alexander (alexand).  Our official support queue is

Keywords:Exchange, migrations, office 365, email, migration, faq, limit, quota, team, group, contact   Doc ID:81374
Owner:Office 3.Group:University of Illinois Technology Services
Created:2018-04-04 08:52 CDTUpdated:2019-02-15 11:12 CDT
Sites:University of Illinois Technology Services
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