I can recieve email but cannot send.
If you can receive POP email but not send it, then it may be that the problem is related to your ISP (Internet Service Provider) blocking the access to our SMTP server. Some big ISPs, such as RoadRunner are known to do this, but the practice is not uncommon. These are the precautions they take to prevent spam email being sent from their networks.
In this case please use your ISP's SMTP server for mail sending. Contact your ISP your to get your SMTP server's address, or visit their website and search for "setting up email." Once you have the correct details (it should be something like smtp.yourisp.com or mail.yourisp.com), you need to change the appropriate settings for sending emails in your favourite email client (Outlook, Mail, Thunderbird) and the problem will be resolved.