MacMail 6.6 isn't sending even tho all systems appear "go"
Of late, my mac mail 6.6 isn't consistently sending e-mails. I've checked with my server (Comcast) and going through their diagnostics all appears to be in order there, so I wonder if anyone else is experiencing inconsistency in sending. I've used MacMail for years, this is the first time I've run into this, on Mountain Lion 10.8.5. Done several tests with regular recipients with mixed results, mostly no acknolwedgement of them receiving.
MacBook Pro, OS X Mountain Lion (10.8.5)