问题描述：Mac 邮箱app添加Gmail账号后，能够收邮件，不能发邮件。
原因：Gmail 认为Mail是不够安全的应用，阻止了登录。
解决方法：
第一种方法直接打开Less secure app access
Google account > Security > Less secure app access
第二种方法，使用 App Passwords
If you use 2-Step-Verification and get a "password incorrect" error when you sign in, you can try to use an App Password.
Go to your Google Account.
Select Security.
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Under "Signing in to Google," select App Passwords. You may need to sign in. If you don’t have this option, it might be because:
- 2-Step Verification is not set up for your account.
- 2-Step Verification is only set up for security keys.
- Your account is through work, school, or other organization.
- You turned on Advanced Protection.
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At the bottom, choose Select app and choose the app you using [图片上传失败...(image-98e536-1601448861294)]
Select device and choose the device you’re using [图片上传失败...(image-d9f450-1601448861294)]
Generate.
Follow the instructions to enter the App Password. The App Password is the 16-character code in the yellow bar on your device.
Tap Done.
Tip: Most of the time, you’ll only have to enter an App Password once per app or device, so don’t worry about memorizing it.
