Yeah, that's definitely unusual.

Have you tried creating a completely new account in Outlook, say for one of your lesser Gmail accounts? Worth a shot…

Since both Outlook & Thunderbird fail, it's unlikely they're the problem. Which points to one of two things:

1. Something on Gmail's end. Check the forums over there, see if there are a bunch of people complaining.

2. Something in your network which is interfering with both Receive & Send. The mention of 127.0.0.1 is interesting, because that's a local address, a sort of 'loopback' when you don't want requests to leave your local network. Here's Wiki's explanation of it.

My top suspicion at this stage is something has gone awry in your network settings. I'm not knowledgeable enough on that subject to offer good advice, but it could be in your router, modem, switch, or your own PC's network card settings.

I assume you can reach the rest of the internet without a problem? Eg websites, download locations etc. So it's not a global access issue, but rather limited to the mail protocols. That I think suggests it's unlikely to be a hardware issue, eg corrupted drivers.

I don't have a clue what could simultaneously impact POP, IMAP and SMTP all at once.

Hmm, a couple of quick things you could try to maybe provide more clues: Setup a completely new account on both Gmail and Outlook.com and have someone send test messages. If both fail, it's almost definitely a problem in your network, as surmised above. If one or both works… then I'm not sure where that would leave us

I'll see if I can roust up a guru to have a peek at this thread, as I'm mostly flailing around in the dark with you.

Btw who's your ISP? It's possible they could be messing with your mail access too—check for complaints on their forums.