mac mail problem since upgrading

I've upgraded to mavericks a few weeks ago. Since doing so I've had a few problems with mail.

I use IMAP on a company server. It works fine on the iPhone and on outlook on my office PC. On the mac it will randomly lose connection to the mail server and not send or receive (usually notice by the choose another server option pops up when sending). The get new mail has a quick flash in the activity window as it thinks there's no connection. Mac book pro, late 2011, i7 2.2GHz with 16Gb ram.

Here's the strange part. Normally when I work on the macbook I use a wired connection for a more stable link, wifi disabled. If I unplug and reconnect the ethernet cable, then the mail works and send perfectly.

It's not a network connection problem as safari still works when mail doesn't, and I can log into the web server of the mail server.

Any time the mail stops working now, I have this quick fix, but it's not right, has anyone else come across a fix for this?