| So, Google has sent you a message that your account is not secure because you are currently allowing less secure apps. It would be simple to think that they are referring to Android Apps.
However, that is only occasionally true.
Most of the time, they are referring to older client programs from desktop computers, clients like Thunderbird or any email client. If you disallow connecting from less secure apps, you will find that you can not access your email.
Kudos to Google for sending a completely misleading email that does not explain the issue. This makes me think back to Microsoft's infamous inscrutable error messages - they never meant what you think they mean.