I'm reaching out here... this has been driving up the wall the last few weeks, as well my users. I have exchange 2003 running on 03 server, in a single domain, multiple domain controller network. Everything works great for people who access email from inside regardless if they use Outlook or OWA. Everything works fine for people using OWA from the outside. Problem comes in when people from the outside use POP. They can only send email to within the company. I have enabled relay for all authenticated users. I have tried everything, on the remote POP machines i checked off, my outgoing server requires authentication, and on the server side.I'm not sure what additional information i should provide. There are tons of things regarding this on the web but i cant find any resolution. I found that you can add each domain who users can send email to, but realistically we have thousands of customers. Any help would be GREATLY appreciated.