Sending of email stopped working

My email has just started to play up. I can receive emails ok but cannot send them. I get the message...

"An error occured sending email. The mail server sent an incorrect greeting. Cannot connect to SMTP server."

Any ideas as to what may be causing this? I am using Thunderbird but the problem is the same with Outlook Express too. The problem has only just started a day or two ago and I haven`t changed any settings.

I`m a bit baffled as to what is causing this.

Jason.

Never mind, it has just started to work again. Must have been a problem at there end.

Jason.

The problem has started again :( Any ideas?

Jason.

Ring up your ISP, and tell them their SMTP server isn't working. There is nothing you can do to fix their server.

So it definetly sounds like a problem at there end then? Just as I thought. Thanks.

Jason.