CRM and Mail Attachment Problem

[DannyvB]

I have a problem sending mails with more than two attachments through the web-based CRM-Client.
I get the error message 'Server error occured. Please contact your systemadministrator'. I am the systemadministrator and I found out that the problem is not the exchange server. It must be the CRM-Server. There are no event-log failures on any server. Sometimes the mails will be send but the attachments are not readable anymore.
Does anyone had this problem before or knows what I can do to fix this problem?
Tanks for help...