Receiving Error 550 when using Exchange via another software application.

Question

Here's a good one (and I hope I'm able to explain this correctly)....
I work at a hospital where we have a gym facility that is open to employees and also to the public.  We use a client management system called Twin Oaks.  This Twin Oaks software has email functionality that uses an Exchange user account to send
group emails out to clients (this avoids the front desk staffers from having to create email distro groups in Outlook to send out mass emails).
I worked with the Twin Oaks support staff to get the email integration set up with our Exchange server (it was an easy process, entering the SMTP server name then a few other basic settings).
Emailing through the Twin Oaks software works, but only to clients who have INTERNAL hospital email addresses.  The messages are failing to go out to any client that has an external email address (Error 550 states the address is unavailable).
Twin Oaks' response to this is that we have some type of firewall that is preventing the delivery of these emails to external addresses.  This is not the case and I can't seem to find any reason that would prevent the mails from going out.  We
can email external addresses direct from the generic account we set up for this purpose, but for some reason, the mails are not going when they are sent through Twin Oaks application.  
We are using Exchange Server 2010.  I can't find any transport settings or policies that would prevent emails from going to external addresses and am stumped as to why this isn't working.  
Has anyone else experienced these types of issues when using Exchange through another software application to send messages?
Any responses would be greatly appreciated!

Answer 1

Hi,
Based on the description, you could send email to external addresses without the Twin Oaks software. However, with the Twin Oaks software, you couldn't send successfully.
For this issue, I recommend you enable message tracking and check whether you could retrieve message tracking log entires when you send emails to external addresses through the Twin Oaks software.
If you couldn't retrieve message these tracking log entires when you send emails to external addresses through the Twin Oaks software, it means that the Exchange server is OK and the crux of the problem is the Twin Oaks software.
Here is an article about message tracking log for your reference.
Get-MessageTrackingLog
http://technet.microsoft.com/en-us/library/aa997573(v=exchg.141).aspx
Best regards,
Belinda
Belinda Ma
TechNet Community Support