Issues with SMTP settings e-Newsletter Plugin

Hi there,

I've installed the e-Newsletter plugin and am using 1and1 for my email.

I have put in the following settings:

From email:
SMTP Outgoing Server:
SMTP Username:
SMTP Password: (password as set up on 1and1)
SMTP Port: 25

After clicking Test Connection I got an error message. Can you tell me where I might have gone wrong?