Exchange Online Message Size Increase

In the Past

Over the past few years I have worked with a lot of Enterprise customers coming to the Office 365 cloud. When specifically working with them on Exchange Online, one of the conversations we would always have is a discussion on message size limits. Up to this point, Exchange Online only support 25 MB message sizes. Most of the time, customers already had smaller message sizes being supported or felt the can do a transition to 25 MB message size. Many cases the need for 25 MB message size was needed or based on old business requirement that could be satisfied through or solutions. Still there would be business cases where customers would have a challenge with 25 MB message size threshold.

So what has changed?

Office 365 has just announced that Exchange Online now supports the ability to send email messages as large as 150 MB.

• Exchange Online administrators have the ability to set the message size to any value between 1 MB to 150 MB.
• The default message size will say 25 MB.
• Customers have the ability to assign some people to larger message sizes, while smaller message sizes can be assigned to different users. This allows customers to align requirements of the business to the configuration of the service.

So how is this configured?

There are multiple different ways to configure this. Inside the Exchange Online Admin Console, administrators have the ability to set the message size restrictions. The message size restriction is actually applied at the mailbox level. You have the ability to change it on individual mailboxes and many at a time. You also have the ability to configure the default mailbox size you want for all new users. Realistically, if you are a large organization, you should you the PowerShell commands that are available to configure this across the mailboxes you manage.

Are there considerations?

Yes there are several things you should consider when setting your strategy for message size.

First, not all other organizations will be able to accept a large email message size. Lots of organizations do not allow receiving of email larger than 25 MB. So really increasing the message size should be for tactical business reasons.

Second, you should consider how SharePoint Online and OneDrive for Business be utilized for sharing files. If the message size is being increased solely for the purpose to allow users to send internal messages with large attachments, SharePoint Online and OneDrive for Business may be a better alternative. Plus SharePoint Online and OneDrive for Business both have external sharing capabilities and can support sharing of significantly larger file sizes. Plus there have new user experiences being delivered between Exchange Online, SharePoint Online and OneDrive for Business that make it even easier for users to share large files quickly and efficiently. I at least recommend that you evaluate these other solutions before just changing the message size to align the business requirement to the technology. Things have changed and there are new solutions.

Third, before increasing the message size restrictions, make sure you understand what the actual mail clients can support. For instance Outlook clients can support 150 MB attachments. However currently Outlook for MAC can support 35 MB attachments and OWA can support 112 MB attachments. This could change in future but this is how they are now. Additionally APIs such as Exchange Web Services (EWS) right now only support 48 MB message sizes and this consideration for customers that are trying to migrate or created other integrated solutions with Exchange Online.

In conclusion

This is a really addition to the Exchange Online service as it provides customers additional flexibility with the configuration of messaging.

Here is the public announcement - http://blogs.office.com/2015/04/15/office-365-now-supports-larger-email-messages-up-to-150-mb/