Office 365 mailbox concurrent connections

Posted on 2013-05-21
Medium Priority
Last Modified: 2013-08-13
Hi All,

Quick question I hope.....

We have a prospective new client who may well be migrating from an old Exchange 2003 in house server to Office 365. Currently there are 12 users who do not have their own mailbox and all connect to a shared mailbox which works fine.

I'm sure I've seen somewhere that standard mailboxes in o365 only allow a certain amount of concurrent connections to the mailbox and was hoping someone may be able to confirm and state exactly how many devices/PCs can connect to one mailbox at any one time.

Many thanks in advance!
Question by:PurpleJelly
LVL 45

Expert Comment

ID: 39185318
According to plan it may vary. Check with MS directly. There are lot of limitation with Office 365. So be aware before moving to it.
LVL 46

Accepted Solution

Vasil Michev (MVP) earned 1500 total points
ID: 39186911
There are different throttling policies for different types of access (OWA, EWS, PowerShell, MAPI, POP3, etc). Unfortunately, they removed the corresponding commands long ago and we can no longer view these settings, let alone change them. The only information I was able to dug out is this:


It is very important to realize that Outlook will use several connections at a time and that the number depends on the mailbox size, folder structure and the number of items in specific folders. Generally, its a good idea to simply create another shared mailbox and move some content.

Another critical point is mobile devices access, especially droids and idevices. Due to the protocol implementation, many of those simply flood the server with too many connection attempts and cause a lockdown. For more info review those articles:


Now, throttling gets significant improvements in Exchange 2013, i.e. the new Office 365, and hopefully the situation will be better there. In the new version, you will also have public folders and the Site Mailbox, so you can work with those instead of using shared mailboxes.

For the situation you are describing, I believe the most important thing is that while shared mailboxes do not consume licenses in O365, only users with Exchange license can actually open them and read/reply to email. So your client might not be happy :)

And if they decide to pay for licenses, those users will have personal mailboxes and you don't have to worry about the throttling.

Featured Post

Simplify Active Directory Administration

Administration of Active Directory does not have to be hard.  Too often what should be a simple task is made more difficult than it needs to be.The solution?  Hyena from SystemTools Software.  With ease-of-use as well as powerful importing and bulk updating capabilities.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

This article explains how to move an Exchange 2013/2016 mailbox database and logs to a different drive.
Organisation is organized in a pattern to flow the day to day business, every application and system is interdepended on each other and when very important “Exchange Server downtime” happened.
Have you created a query with information for a calendar? ... and then, abra-cadabra, the calendar is done?! I am going to show you how to make that happen. Visualize your data!  ... really see it To use the code to create a calendar from a q…
This lesson discusses how to use a Mainform + Subforms in Microsoft Access to find and enter data for payments on orders. The sample data comes from a custom shop that builds and sells movable storage structures that are delivered to your property. …

624 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question