The problem that you are reporting does not look like the Windows SSL buffer size problem. Your sample shows that the server does not offer MULTIAPPEND, so each message is being appended individually. The previous message was appended successfully (the "APPEND completed" response). It then ran into trouble appending a 2750 byte message, which is much too small to trigger the Windows SSL buffer size problem.
The Windows SSL buffer size problem is caused by receiving a SSL encrypted block of greater than 16379 bytes (16K - 5 bytes). SSL allows the block to be a full 16K, but Microsoft's SSPI mistakenly counted the 5-byte header against this total. Your transcript indicates that, from c-client's point of view, the Exchange server unilaterally closed the connection. It sent the 2750 message bytes, and was waiting for an acknowledgement of completion when instead it got an error reading from the server. Perhaps the Exchange server has logs related to the incident which may be of help in diagnosing the problem further. -- Mark -- http://staff.washington.edu/mrc Science does not emerge from voting, party politics, or public debate. "A single glass of champagne imparts a feeling of exhiliaration. The nerves are braced; the imagination is agreeably strirred; the wits become more nimble. A bottle produces a contrary effect. Excess causes a comatose insensibility. So it is with war; and the quality of both is best discovered by sipping." -- Winston Churchill
