SMTP server down?

Today all of a sudden, I am not able to send out emails through Dreamhost’s mail server using Outlook. In the Send/Receive window, Outlook reported “Processing” for a long time, then it timed out and gave this error:
"Task ‘ - Sending’ reported error (0x800CCC0F): ‘The connection to the server was interrupted. If this problem continues, contact your server administrator or Internet service provider (ISP).’ "

However, I am able to receive mails.

Is the SMTP server down (for the whole day?) or am I doing something stupid?