Problem With SMTPMail. Can't Send To Email Outside Domain

Good day.

I faced a very weird problem regarding the SMTPMail component. ACtually I am maintaining a system previously done by somebody else which has left. The problem only occured since today.

It's an web application using ASP .Net. Let say the domain name is ABC.Com. If I tried to send email to [email protected] to [email protected], it works regardless whether I am using ABC.com SMTP server or other external SMTP server.

However, if I tried to send to some other email outside the domain, it fails.

It only happen in ASP .Net web application. I tried using ASP, it works. I don't think is a problem with the web app source code, as previously, the system is working just fine. No changes was made on the server setting and the source code and previously it worked.

Is it possible because of the firewall setting ? or SMTP server setting?

Thanks.

SonicWave :p