I have one user who is unable to send an email to a recient that anyone else in my company can send to. the undeliverable happens with a couple seconds. It is as follows: The following recipient(s) could not be reached: 'someone@somewhere.com' on 9/18/2008 4:55 PM The message could not be delivered because the recipient's destination email system is unknown or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email system of the recipient. <smtp.myserver.net #5.1.2> Any help would be appreciated. i have had 2 It consultants look at this and both cannot provide an answer.

Hi, There has to be something wrong when this user sends the mail. Is the user using a contact object when sending? Has the user tried to use the SMTP address? Has the user tried to send using OWA? Leif

Hi, This issue can be caused by the bad contact object or a corrupted cache name in Outlook. Please type the complete email address and test the issue again or you canrename thename cache file of Outlook.A similarthread for your reference: http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=2481122&SiteID=17 Please also use OWA to test the issue and let us know the result. Hope this helps. Thanks, Elvis