Dakoolist's suggestion did not resolve my problem of sending emails and my SMTP being "offline". This is what solved my problem, bear in mind that I am using OSX 10.8.1, so these steps may not be exactly what you see in your Mail program if you are working with an earlier version of OSX.
Mail Program - click on Preferences
Assuming all information on this main page correct, I went down to where it says Outgoing Mail Server (SMTP). If you hold down the bar to the right, one of the choices is Edit SMTP Server List. Choose this.
After I chose Edit SMTP Server list, at the next window half way down the window it says "Account Information" or "Advanced". Choose Advanced.
Once I opened this Advanced window, all my problems were here, as nothing was filled in! I had to choose "Use default Ports (25,465,587). I had check "Use Secure Sockets Layer (SSL), then I had to choose "Password" as the type of Authentication, and I had to fill in my user name and password.
Once I filled everything in here, my issue of sending emails was resolved. What had me confused is that there are actually TWO DIFFERENT places within Mail Preferences where you check the SSL box...once for Incoming and once for Outgoing Mail.
This resolved my problem; Hope it solves yours.