Mail Disconnects and Reconnects

I'm finding that Mail will all of a sudden disconnect from one or all of my email accounts and then reconnect. Sometimes I do something like quit and relaunch which may (or may not) help. Other times I do nothing and wait and the reconnection happens. I started writing this question when most of my accounts were offline and I just checked them and now they're reconnected again. Nothing I can find seems to be the same issue, much less why is it happening. Does anyone else know what this is?