Running OS X 10.11.4 on 2012 Mac Mini Server (6,2). Apple mail will not send mail - SMTP Server shows as Offline. I have repeatedly checked all setup parameters. Same setup works on iPad & iPhone. I have researched on web and tried all recommended solutions short of manipulating files in V2 and V3 folders, which I am not comfortable with. Deleted & rebuilt accounts, deleted and rebuilt keychain entries, confirmed setup with ISP. SMTP does work on my Verizon account but not with Google or iPower.com accounts. All worked fine under Mavericks. My OS X is an upgrade from Mavericks, not a clean install, if that matters. I have done all steps in the Apple trouble shooting guide. Anyone got a solution?