Exchange SMTP relay problem! Plz Help

I have two problems that relate. First lets start out with that i have, I have a single domain with active directory with dns. Yet i have the exchange server off site for various reasons (dont let other employees touch things they arnt supposed to when they dont understand them and they are critical). When i use SMTP locally to my external exchange server, i receive the emails just fine (it routes locally somehow?!). When i use the SMTP locally to a different email exchange server such as yahoo or gmail, i get an error and it wont allow me to relay the message.
Then for another instance if i use a virtual smtp server in IIS and try to relay message to my exchange server i cannot receive it. YET! then when i try to relay a message from that virtual smtp i can receive message on my yahoo or gmail account.
The only thing i can come up with is that there must be something weird going on with Active Directory or something. Cause i talked to the techs that host my exchange server and they opened up all the ports for me to allow me to test the relay and i still cannot receive messages (I know unsafe but it was just a test to see if there was something blocking it).
PLEASE HELP!

1. Check that you are allowing relaying to external domains and that DNS is correctly configured

2. The IIS virtual SMTP service will probably be sending mail directly (hence your Exchange problem is not effecting it).