I have a fully functioning SMTP server. This server has no issues with mail delivery except when the email address is a cellular provider. Our monitoring system attempts to send email to XXXXXXXXXX@tmomail.net and the SMTP logs a 550 error. The email address is valid and if you send to that email address from a local outlook client the email-SMS conversion occurs without issue. When our applications send alerts using the exact same email address it recieves a 550. Anyone else experiencing this issue? Any thoughts/ideas as to why it would result in an error?

Hi, As this issue is related to IIS, I suggest discussing it in our IIS forum. They are the best resource to troubleshoot this issue. http://forums.iis.net/ BrentPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.