I can receive email but I cannot send outgoing mail

Email > Troubleshooting email problems and errors
In some cases when you attempt to send mail you can experience an error similar to the following:
The connection to the server has failed. Account: 'John@yourdomain.com',Server:'mail.yourdomain.com', Protocol:SMTP, Port: 25,Secure(SSL): NO Socket error: 10061, Error Number: 0x800ccc0e  
This error usually indicates the failure of youremail program to connect to port 25, the SMTP (outgoing mail) port. One of the following is the likely cause of this problem:
  1. Your firewall blocks SMTP connections to an internet mail server. Consult your firewall documentation or network administrator for details.
  2. Your Internet Service Provider (ISP) does not allow SMTP connections to an internet mail server. Most large ISPs now block port 25 in an effort to prevent spam. If you believe that this is the cause of your error you can configure your SMTP port from 25 to 8889.