We have a server in Michigan and one in Arizona that might be trying to log in to your email account. Google's security will sometimes decide it looks suspicious.
A couple things you can try when this happens. It may take more than one of these steps to fix it:
If not using two-factor authentication
1. Go here and set it to ON: https://www.google.com/settings/security/lesssecureapps
2. Go here and follow the instructions: https://g.co/allowaccess
(the above steps were taken from this page: https://support.google.com/accounts/answer/6009563)
If using two-factor authentication
Choose Mail on my Other (Custom name) and type IO and hit generate. Copy the password into the software under Settings --> Email Preferences.