Exchange supported authentication types are:                                              

integrated windows (NTLM)
digest
basic
.NET

JEC Supports digest and basic authentication schemes.
.NET and NTLM are not supported.

NTLM digest and basic can all be supported simuntenusly by Exchange.
all conbinations will work except NTLM & digest (and ofcourse NTLM alone will not work, as mentioned above)


authentication scheme           supported
=====================           =========
NTLM                               false
NTLM + basic                       true
NTLM + basic + digest              true
NTLM + digest                      false
basic + digest                     true
digest                             true
basic                              true

There is another "authentication" type (which is not really authentication type per se) 
called by microsoft "forms-based authentication" (or FBA).
in case this is on, JEC will not work and return exchange error 440.