can anybody solve this problem for Voice communication through ISA. I have a strange problem with ISA. I have configured H.323. When external user send a voice invitation through MSN Messenger, it works perfectly but if internal user want to send the invitation to external users it cannot establish connection. and same problem with File transfer. if both the users are internal and doing voice chat through MSN Messenger so it works with no error. Can anybody solve my problem ? Khurram Khan System Engineer Alnafitha IT Tel: +966 2 652 1112 Fax: +966 2 652 8151 Mail to: khurram@xxxxxxxxxxxxx <mailto:khurram@xxxxxxxxxxxxx>