asp.net email with relaying blocked

[jplahitko]

I am writing an internet application using VB.net and ASP.net that allows customers to search our MSSQL database and request transfer of a selected asset. The submit button prints a delivery receipt and emails customer service within our company. During off hours, I want it to also email the "on-call" phone. We use MS Exchange with relaying blocked. The cell phone email produces an error indicating it cannot relay. Is there a workaround to allow the application to email back out of our domain? I welcome any ideas.

 

[jplahitko]

I should have added the error message received:

The server rejected one or more recipient addresses. The server response was: 550 5.7.1 Unable to relay for someone@somewhere.net

 

[MichaelPerry]

I think you can set up exchange to allow relaying from certain ip domains(ie your own) but you need to be carefull. Turning on relaying is not something you want to do for a public mail server as it is a security risk. The options are in the routing(routing restrictions) area of the Internet Mail Service.

Alternatively... You could set up the smtp service that comes with IIS on a different machine and alow relaying on it. It can only send emails but in your .net app you can set the reply address as you normal email domain which will return replies to your exchenge server. I've actually used this method to create a simple web service on our web server that I can call from any .net app I write.

 

[jplahitko]

Thank you Michael for your tips. Our consultant suggested the same approach so we allowed relaying from the machine running the .net apps and so far it seems to work fine.