Exchage 5.5, about a month or so, began to report errors "email address not found" of recipients who have good adrresses and used to receive email from the same email server a few months ago? Here is what I get: The recipient name is not recognized The MTS-ID of the original message is: c=us;a= ;p=builderdepot inc;l=CYBERMAIL0205270556LM6WZSLL Another error sample: did not reach the following recipient(s): goodidea@xxxxxxxx on Sat, 25 May 2002 18:39:18 -0700 Unable to deliver the message due to a communications failure The MTS-ID of the original message is: c=us;a= ;p=builderdepot inc;l=CYBERMAIL0205260139LM6WZSF8 Another email sample: psw56@hotmail on Mon, 6 May 2002 13:32:43 -0700 Unable to deliver the message due to a communications failure The MTS-ID of the original message is: c=us;a= ;p=builderdepot inc;l=CYBERMAIL0205062032GWB5X2K3 MSEXCH:IMS:Builderdepot Inc.:BUILDERDEPOT:CYBERMAIL 3902 (000B09AA) Host Unknown Another email sample: maqsood@xxxxxxxxxxxxx on Mon, 13 May 2002 10:46:52 -0700 The recipient name is not recognized The MTS-ID of the original message is: c=us;a= ;p=builderdepot inc;l=CYBERMAIL0205131618GWB5XKK2 MSEXCH:IMS:Builderdepot Inc.:BUILDERDEPOT:CYBERMAIL 3550 (000B09AA) 550 <maqsood@xxxxxxxxxxxxx>... User unknown