Binary package hint: evolution
System->Preferences->Network Proxy has a web proxy set, and if the 'Use the same proxy for all protocols' checkbox is selected, Evolution attempts to connect to a non-existant socks proxy when trying to reach an IMAP server. This is a change in behaviour from Maverick.
Initial symptoms are that Evolution hangs when trying to reach the IMAP server - `tcptrack -i eth0` and strace show connections to the configured http proxy, and then an IMAP connection to 127.0.0.1. Unchecking the 'use the same proxy for all protocols' box and individually setting the proxy for the other lines fixes the issue.
This occurs even when Evolution has 'Direct connection to the internet' set in its own Network Preferences.