Exchange & ML - Email Attachments

I have read a lot about the trouble others have with ML & Exchange.

I came across a very similar problem: Since I upgraded to ML I cannot send any more attachments bigger than 50 kb via Apple Mail using my exchange account. It works fine if I use my Gmail or iCloud email account.

Receiving emails from my exchange account with attachments is however not a problem.

I checked with my admin if my exchange server account is subject to any size restrictions but he confirmed that I can send attachments up to 5 MB.

It is a pretty annoying problem as I work a lot with documents and have to send attachments a few times per day.

Has anyone observed the same problem? If yes, any idea how to fix it?

Cheers

Baba