After originally posting this issue on the MS Community Forums, it was suggested by MS Support Engineer Ratandeep that I post this issue in the TechNet forum for additional assistance...

Issue Description:

I have a client using Windows Mail on a Surface Pro tablet running Windows 8.1. From the Windows Mail client, they are unable to send messages with attachments greater than 5 MB in size. If I have them send via Outlook, there's no issue. Based on the Transport Settings configured on our Exchange server, we should be able to send a 50 MB attachment.

Does anyone know of a registry key that can be added (similar to the one for Outlook) that will configure Windows Mail to allow for larger attachments?

Additional information:

You asked: Is Surface Pro connected to a domain network?

-- Yes, it is connected to a domain network. Sometimes on the local wireless network, and other times through a VPN connection. Please note: On our Domain Exchange server, the Transport configuration allows the sending and receiving of attachments of 100 MB or smaller.

You stated: This issue may occur due to corrupt mail app files or settings.

-- If the currently installed app was "corrupt," wouldn't installing the latest version (which I did) fix that issue? As far as settings, I haven't seen any setting in the client or the registry regarding attachment size.

You stated: The maximum size of the file which can be attached in a message in mail app is 25 MB.

-- That's what I had read during my research of the issue, but this user is clearly experiencing an issue with attachments of 5 MB or larger.

• Edited by R.Doyle.5Below Tuesday, May 05, 2015 1:38 PM