SOH character (hex 0x01) is not a valid character in XML. Since EWS uses SOAP which is XML based protocol, and the subject value is send in a XML tag, this results in that failure. Furtunately, this character check can be turned off, so we can make a hotfix for you. If you have a valid licence, please let us know on firstname.lastname@example.org and we will send you full version of that hotfix. I will post a link to a trial version of that fix here on the forum today.