I can receive emails but can't send it

I urgently need a help and find out what the problem I faced with and how I can find a solution very fast.

For the first time I see this, that I can't send emails from my apple mail (it's always left in my outbox) and this is what it said in its top the right corner: "Connections to the server “p50-imap.mail.me.com” on the default ports timed out."

What should I do, maybe you know? Please help me as soon as you can