Here are updated instructions if you are looking for Exchange 2013: http://www.iishacks.com/2013/04/26/configure-exchange-2013-to-send-external-email/
So you can’t send email from a fresh install of Exchange 2010? Unlike Exchange 2003, Exchange 2010 cannot send emails to external domains out-of-the-box. This feature needs to be enabled through the use of an external send connector. By default, no send connectors are configured when an Exchange 2010 system is setup with a hub transport or edge transport role (typical installation). At first it seems odd for an Exchange server to not allow external email sending by default, but this is commonplace in insurance and financial institutions where complete control over external communications is necessary. I’ll walk you through the steps to create an internet-facing send connector which will allow you to send email to any external domain.
1. Open up the Exchange Management Console. Double-click on Organization Configuration and click on Hub Transport. Click on the “Send Connector” tab. Either right-click on the whitespace or select “New Send Connector” under the Actions task list.

2. Enter a name for the send connector. Under intended use, select “Internet” in order to send to external domains. Click Next.

3. Under Address Space click “Add…” and select “SMTP Address Space…” Click Next.

4. Under SMTP Address Space -> Address, put a * (asterisk) in order to send to all external domains. This is where you may wish to customize the address space by only allowing external emails to specific vendors or customers. Click OK, then click Next.

5. If you are using a smart host to route your emails (sometimes required by an ISP), configure it here. Otherwise, check “use domain name system” to route emails (typical). Click Next.

6. For a single-server installation of Exchange 2010, the source server will be the only one in the list. If you have multiple servers with a hub transport role installed in your organization, you can select a specific server to use. Click Next.

7. This is a summary page of the send connector. Click Next.

8. After the send connector has been configured, this page will appear. The syntax shown is also the powershell equivalent to what was run. Click Next.

9. Once the send connector has been created, you’ll need to configure one last item. Right-click on the connector and select “Properties.”

10. In order to get past some of the more strict spam filters, you need to configure the Fully Qualified Domain Name (FQDN). This is typically the internet-facing address of your email server. Click OK. You’re ready to send email to external domains!

IT Guy
Excellent walk through of the Connector setup. Besides creating an SPF record, which you have covered, readers should also take a couple extra steps to help ensure that their mail gets delivered timely and has the lowest chance of getting marked as spam.
Make sure your mail traffic comes from a different Public IP address than your browser traffic
Public forward and reverse records in your Public DNS for send connectors
Long term, readers may want to Configure Public TLS as well.
Again, great walk through.
Diego
Thank you for this, I had never worked with Exchange 2010 so I had to learn it quickly. Through your screen shots I managed to figure out why my mail was not going out.
Cheers!
-Diego
Neilrahc
Thanks a lot – clear and simple. It bridged my knowledge with how SMTP connectors are configged in 2003.
Hosam
Thaaaaaaaaaaaaaaaaaaanks
rabbit7
Great work, configuring right now
Joey D
Great job.. thanks for the help !
Tom Merritt
One of the best walkthroughs I’ve seen. Thanks! I especially like your use of yellow highlights to indicate user input, and since imitation is the most sincere form of flattery, I’m gonna use that myself!
I figure I owe you, so if you’re ever anywhere near Rochester, NY, I’ll buy ya a beer,
gman
Wow nice work… thanks!
mihai
Hey! nice work!
Can you tell me if there is a configuration for receiving mail ?
after i have done step be step your tutorial i can send email but i cant receive.
can you help me you some advice ?
Ty!
xurc
Thank You, Thank You, Thank You. Why couldn’t Microsoft do that?
Chris Stinson
Having it disabled by default prevents Exchange from becoming an open relay as soon as you install it and haven’t had time to lock it down. Good for sloppy admins.
As an aside, many large organizations have external emails disabled – they only use exchange as an internal tool. Although I can’t imagine Microsoft did it for that reason.
Jonathan
I’m at the point where I’m trying to create a send connector and the tab for send connectors is missing in the Exchange console altogether. Using RBAC, I’ve confirmed that my account is in a group that should have that right, so I don’t understand what is going on.
Chris Stinson
I’ve had this happen before. The management Group did indeed have that right assigned, but the User that was logged into the console was not in that group (accidental).
Try removing and re-adding the User or even the rights to that Group.
Jason
So I did this, and my mail server is still not sending to external domains. I can recieve email fine, but I can’t send to any internet domains. Any idea on what’s going on?
Romeo
Thank you, just what i needed.
myrick
this is great… thanks mate…..
hopefully, please do make
External mails to inbound….
with DC-DNS Config.
Thanks….
sokha
now i have a problem. who can help me to solve the problem? i configure email already and testing in local is send to know is together.but when i send email external (yahoo) to exchange server (mail exchange) is failure? what should i do about like this?