Gmail just alerted me that my Gmail account was accessed from this IP address "184.108.40.206" and that leads to
Redmond, Washington, USA and the ISP (owner) is Microsoft.
How can this happen? It's really weird.
Please try the Gmail Security Checklist. In particular, make sure your account isn't compromised. Also, there are instructions to check for authorized applications. If you are using an addon, extension, or other third-party application that you gave access to your Gmail account, you might see strange activity.
The owner is Microsoft Dynamic hosting, so probably an Azure instance. Gmail doesn't do "mistakes" like giving you wrong information. (At least I haven't seen it do any.)
It is plausible someone got hold of your password and tried to access it from an Azure instance to avoid being tracked.
Another point, if you use Hotmail—Hotmail can fetch mail from other servers via POP—, it's possible that the IP recorded is that of Hotmail's fetch process.
If you haven't used Hotmail, I'd urge you to change your password ASAP.