TLDR: OS X El Capitan 10.11.5, Mail.app, Gmail, 2013 Retina MacBook Pro. Mail randomly refuses to send and/or receive mail. I've tried everything I could find online about this exact issue, nothing has helped so far. I think it was fine in Yosemite, it was definitely fine in Mavericks and before. So someone calls me and says "hey did you get my email?". I say "no, let me refresh it just in case", and press the "Get Mail" button in Gmail. It says "Checking for mail...". It says that for far too many seconds, and nothing happens. So I go to Gmail.com, which I rarely do, and I find a new message, sent 2 hours ago. 10 minutes later, Mail still says "Checking for Mail...". This happens all the damn time. Sometimes it works, but when I have important stuff to do, it doesn't work. I sometimes send a message and it says "Sending..." for about 10 minutes, then I cancel it and send it again. Then both messages get sent eventually even though both are sitting in Outbox. So I think it's still not sent, and delete the message and resend it from gmail.com. Then it gets sent 3 times in total, which I only find out much later, when mail finally removes it from Outbox. Then I get exclamation marks next to my Inbox in Mail. When I click on it it says something about outgoing mail servers, which I have checked and is correctly set up (as proved by the fact that messages do eventually get sent). I have deleted all the mail cache, I have turned off my gmail account in OS X, I have deleted everything from Mail and started from scratch. I have done this 3 times so far, no luck. I'm out of ideas. How do I send and receive emails with Mail? I may have 10 years of experience with complicated software but I'm probably too ****ing dumb to figure out how to send a ****ing email with the "world's most advanced operating system" (don't make me laugh). I'd post screenshots but I just deleted my entire mail account so there's nothing there. Could someone please just tell me how it's supposed to be set up with Gmail for it to actually work without any issues? Also, could you recommend any free apps that are as much like Mail as possible, except they actually work?