I installed Exchange Server in a virtual machine a while ago to play around with it and see if I could get the mail server to work properly. I thought I was fine because I could send and receive messages on the network and be able to send emails to the Internet.
However, when I logged on to a computer external to my network using Remote Desktop and tried to send an email to the account I created on the Exchange server, I received the following message:
You have no permission to send to this recipient. Contact your system administrator for assistance.
Then there is some kind of message relay error:
Please note, if you came to this page because you are trying to send someone an email and you are not sure if it is a problem on your side or on the recipient’s side, then it is definitely a problem on the recipient’s side! In this case, you need to call the person you are trying to send an email to and ask them to notify the network or email administrator of the problem.
This is essentially an Exchange Server configuration issue that needs to be fixed. Therefore, if users in your domain cannot receive email from outside the internal network, here’s what you need to do.
Fix the drain issue
Step 1. In Exchange System Manager, expand Servers, expand Protocols, and then expand SMTP.
Step 2. Select the SMTP virtual server that you are using to connect to the external network, right-click and select Options or Properties.
Step 3. On the “Access” tab, click “Relays”.
Step 4: First select List Only below. Now you need to uncheck the “Authorize relay for authenticated computers” or “Allow all computers that successfully authenticate to relay” checkbox, click the “Users” button.
Step 5. Select the “Allow” checkboxes for authenticated users (permission to post and permission to reply).
This is it! Now all you have to do is start and stop the SMTP server from the main console window in Exchange! External users should now be able to send emails to your domain without receiving “Unable to relay” or “You do not have permission to send to this recipient” error messages. Enjoy!