Dear Experts, IMAP/SMTP , Exchange Server 2003 (frontend/backend) I have exchange server 2003 frontend/backend topoligy. Email functions very well if we are using mapi,https,rpc over http.But if we configure IMAP client to send mail from outside our organization i.e from internet we are getting below error.But if we send mail from inside our organization 10.10.1.0 network everything works fine.In outlook setting-I enabled my outgoing server require authentication.If I dont select that I even cannot send mail from our pc connected with the same domain also.I also enable imapuser in-- default smtp virtual server-access-relay-users-abc user. Below is the error from outlook IMAP: Task 'imapuser@abc.com - Sending' reported error (0x800CCC80) : 'None of the authentication methods supported by this client are supported by your server.' If I uncheck my outgoing serve require authentication I get below error when the outlook is connected with internet Your message did not reach some or all of the intended recipients. Subject: test Sent: 3/7/2013 8:25 PM The following recipient(s) cannot be reached: 'someid@gmail.com' on 3/7/2013 8:25 PM 550 No such domain at this location Kindly advice. Thanks

Software/Hardware used:
Exchange server 2003