This happens about once a week or so. Using OS X 10.9.5 Gmail will work fine, both sending and receiving (using IMAP) and then all of a sudden a message sits in the Outbox. Error is that "the connection to the server smtp.gmail.com timed out on the default ports". Note - I can still receive emails just fine. Connection doctor shows nothing odd - just that it tries to connect to smtp.gmail.com and won't. I've tried quitting and restarting Apple Mail, taking all mail accounts offline then online, editing my gmail smtp server username and password - all the things I've seen in various posts online that claim to have "fixed" the problem for the posters...none work for me. The only thing that has worked (so far every time) is to restart my Mac. It works, but it's a PITA to have to close all my apps and restart to send an email. Any ideas what a restart is doing that is clearing this up and how I could mimic it without doing a restart of the entire machine?