If Outlook is receiving email but you are getting an error when you send, it could be that your port is being blocked.
- Open up Outlook
- Go to Tools < email accounts or Account settings
- Double click on your email account or select and edit
- Select More settings on the Internet E-Mail Setting Screen
- Select the Advanced Tab
- Change your Outgoing server (SMTP) Port from 25 (this can be blocked) to 587
Update a login email address