Since last year, TmNet (Malaysian ISP) gradually blocking access to SMTP port – 25 to combat spam coming out from their network. If you are one of the subscribers and having problems sending out email you can modify you outgoing SMTP server port to 26. You can follow guidelines below for Outlook Express.
For Outlook Express,
Make sure you enable SMTP Authentication
Tools> Account > Mail > Highlight email account and Click Properties and check My Servers Requires Authentication
To change SMTP port, click advance tab and change 25 to 26