Google’s Gmail provides a free SMTP server, it can be utilized by anybody who has a Gmail account.
Any case you don’t have a Gmail account, you can create a Gmail account.
Then all you need to do is configure your mail client to utilize GMail for the outgoing mail server. The details you should utilize are:
Outgoing Mail (SMTP) Server: smtp.gmail.com
Use Authentication: Yes
Use Secure Connection: Yes (this can be TLS or SSL depending on your mail client)
Username: your GMail account
Password: your Gmail password