I've got quiete a shitty problem. I deverlopped a program for a customer to pick up mail from a POP3 server and sends it through to a mailing list via an SMTP server. The SMTP server and POP3 server are both a MS Exhcange Server 5.5. I connect to the POP3 and SPTP server with TNMSPTP and TNMPOP components delivered with Delphi. I can connect without any problem to this server. However, when I send an e-mail and the recipient is not in the adress book of the MS Exchange server, he gives the error : Unknown recipient. When the person filled in in ToAdress is a person from the domain itself (In this case vau.nl) then the mail is delivered good. When I send it to another domain, let's say for example Tom.Dedecker@tijd.com, then I got the above error message. Anyone who had this same problem or has any suggestions. I tried already quiete some things qnd my knowledge of exchange is not that good. Important : If I configure OUTLOOK to send an receive e-mail then I can send e-mail to other adresses without any problem. This is quite a hard and urgent problem so all tips, suggestions, .... are welcome.....