Cannot send email with large attachments in .NET 4.5

Hi,

I have a .NET application that sends emails with large attachments. Almost a year back when I deployed this application, our production server was on .NET 4.0 framework. I found this problem early and was able to fix it by installing "support.microsoft.com/kb/2468871/en-us" update, which lists that it fixed the issue KB2183292.

Recently, we upgraded the production server to .NET 4.5.1 framework (which is an in-place update). After this install, the problem is back and I am not finding any hotfix for .NET 4.5.1 for this issue.

Please help.

Thanks.