Apple Mail - all accounts offline
Without warning all of my email accounts are completely offline on my MacBook Pro running Mavericks 10.9.3. My Mail version is 7.3.
I cannot send or receive. Clicking on "Take all Accounts Online" has no effect, and doesn't even bring up an error message or info box. It might possibly have happened after the mac was asleep, but hard to tell - I just noticed it in the middle of the day when I hadn't had any mail for a while.
I have quit and re-opened Mail a few times, re-started the mac a couple of times but neither of those helped. The connection doctor gives everything a red blob. And I definitely have a network connection.
I can get Mail for all the same accounts on my iPad and iPhone, so the problem is not with the accounts, and they are a mixture of POP and IMAP accounts with various providers, so no common theme.
Any ideas as to what I should try next?
Cheers