Since yesterday I can't send any emails. They alway stay in my sending folder, after a few minuts I get a server timeout message. I tried it on my MBP (Mavericks) and iPhone (latest firmware). Does anybody else have this problem?
You might try going to System Preferences>iCloud on your Mac, uncheck Mail, restart your Mac, then go back and check Mail again. On your iPhone, go to Settings>iCloud, turn Mail off, then after a miniute or so turn it back on.