Evolution not sending or receiving mail
 

I've recently had my broadband connection down, and after the service was restored I found that I could no longer use Evolution. The send/receive button is greyed-out as unusable.

My connection is fine: I can access the internet. I've tried pinging my ISP's mail servers and they respond. So what's happened to Evolution?

It's probably in offline mode. Look in the lower left corner, there is a little button with a "plug" on it. Click it to go online again.

So it is! :redface:

I presume it took itself off-line when it couldn't find a server: very clever, but I wish it had told me.

It depends on network-manager. Whenever network-manager does not see a network connection, evolution will start in offline mode. This is (unfortunately) also true if you have working, but manually configured connection, that is not managed by network-manager. Evolution will then always start offline, even if you disable the option in gconf. You then have to uninstall network-manager or let it manage your connection.
Very annoying thing ...