Unable to send emails

[Goofy]

I've been using Mozilla thuderbird for a few years with no problems. Quite suddenly I can no longer send emails, although I am still receiving them. I haven't changed anything on my pc - but I get the message

Sending of message failed.
The message could not be sent because connecting to SMTP server faild.
The server may be unavailable or is refusing SMTP connection. Please verify the SMTP servier setting is correct and try again.

[ChrisDean]

This is possibly due to a change with your ISP's mailserver or possibly your smtp port being blocked, though the former is the most likely answer.

Call your ISP or visit their website and check that your SMTP settings are in fact correct.

[Goofy]

I suddenly thought of using the 'restore' in windows and that worked. Still don't know what happened, but at lteast I'm back in business